Comet Publications Used in Preparing
the 2005 Triennial Report
The ADS abstract service (http://adsabs.harvard.edu/abstract_service.html)
was searched for papers appearing in refereed publications during the period
between July 2002 and June 2005, inclusive, on the term "COMET". This
returned 917 abstracts plus 37 papers published in the Comet II book that are
not considered to be refereed papers by the ADS.
From these 954 papers, 361
were selected as falling under the purview of the Physical Studies of Comets
Working Group. That is, no papers on purely meteoritic, interplanetary dust
(including cometary trails), dynamical, or astrometric
studies were included. Papers presenting
ground-based instrumentation or space instrumentation or missions for future
comet studies were not taken into consideration either. However, papers
presenting laboratory experiments for the understanding of the origin of
cometary material were included.
The 361 relevant papers were
sorted into nine categories and a brief description of the scientific results
in each category was written citing a subset of them. The titles and abstracts
for the entire list of 361 papers appear below. The order of this list is that
returned by the ADS search engine, i.e., it is not in alphabetical or
chronological order. A paper cited in the IAU Triennial Report can be located
using the browser or PDF reader’s “Find” function.
This list was prepared by D.
Bockelée-Morvan on 20 September 2005
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Title: |
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On the ejection velocity of meteoroids from comets |
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Authors: |
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Affiliation: |
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AA( |
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Journal: |
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Monthly Notice of the Royal Astronomical Society, Volume 337, Issue 3, pp. 1081-1086. (MNRAS Homepage) |
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Publication Date: |
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12/2002 |
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Origin: |
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MNRAS |
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MNRAS Keywords: |
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comets: general, meteors, meteoroids |
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Abstract Copyright: |
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(c) RAS |
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DOI: |
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Bibliographic Code: |
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2002MNRAS.337.1081M |
The ejection of meteoroids from comets has been discussed by many authors and is a problem that is important both for a full understanding of cometary processes and for the evolution of meteoroid streams. We reinvestigate the problem here, starting from simple physical principles, and compare the results that we obtain with those of other authors, in particular Whipple.
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Title: |
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Erratum: On the source of C(1D) atoms in cometary comae |
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Authors: |
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Journal: |
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Monthly Notice of the Royal Astronomical Society, Volume 337, Issue 2, pp. 768-768. (MNRAS Homepage) |
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Publication Date: |
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12/2002 |
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Origin: |
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MNRAS |
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MNRAS Keywords: |
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errata, addenda, molecular processes, comets: individual: Comet Halley, comets: individual: Comet West, comets: individual: Comet Bradfield (1979 X) |
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Abstract Copyright: |
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(c) RAS |
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DOI: |
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Bibliographic Code: |
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2002MNRAS.337..768S |
Not Available
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Title: |
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X-Ray Emission from Comet McNaught-Hartley (C/1999 T1) |
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Authors: |
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Krasnopolsky, V. A.; Christian, D. J.; Kharchenko, V.; Dalgarno, A.; Wolk, S. J.; Lisse, C. M.; Stern, S. A. |
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Journal: |
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Icarus, Volume 160, Issue 2, p. 437-447. (Icarus Homepage) |
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Publication Date: |
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12/2002 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
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(c) 2002 Elsevier Science ( |
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DOI: |
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Bibliographic Code: |
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2002Icar..160..437K |
Comet McNaught-Hartley was observed in five 1-h exposures on January 8-14 2001 using the advanced CCD imaging spectrometer on board the Chandra X-ray Observatory. The X-ray image of the comet does not show a crescent-like shape. The brightest region is offset from the nucleus between the sunward and comet velocity directions. The comet mean X-ray luminosity is equal to 7.8×1015 erg s-1 for photon energy E>150 eV and aperture ρ=1.5×105 km where the comet X-ray brightness exceeds 20% of the peak value. Gas production rate was 1029 s-1 during the observations, and the efficiency of X-ray excitation was equal to 4×10-14 erg AU3/2. Day-to-day variations in X-rays reached a factor of 5. The strongest short-term variation was by a factor of 1.75 for 1600 s. This variation may be explained by a decline in the solar-wind flux by the same factor in ~800 s. The comet and Earth were seeing different faces of the Sun, and time delay in the solar-wind events on the Earth and the comet was long, equal to 6 days. The best correlation between the comet X-ray luminosity and the solar-wind proton density is for the time delay of 5.5 days and may be explained by the higher velocity of heavy ions. Careful background subtraction made it possible to extract the comet spectrum from 150 to 1000 eV. No signal was detected at E>1000 eV, and a 3σ upper limit to any emission with E>1000 eV is 0.3% of the photon emission at 150-1000 eV. The best χ2-fit model to the spectrum consists of nine narrow emission features. The emission energies and intensities are in good agreement with a charge exchange spectrum calculated by us for the slow solar wind. Using this spectrum, we identify the observed emissions as (Ne7++Mg7++Mg8+) at 195 eV, (Mg8++Mg9++Si8+) at 250 eV, C5+ at 370 and 460 eV, O6+ at 560 eV, O7+ at 650, 780, and 840 eV, and Ne8+ at 940 eV. X-ray spectroscopy of comets may be used to diagnose the solar-wind composition and its interaction with comets.
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Title: |
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The Dust in Comet C/1999 S4 (LINEAR) during Its Disintegration: Narrow-Band Images, Color Maps, and Dynamical Models |
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Authors: |
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Bonev, T.; Jockers, K.; Petrova, E.; Delva, M.; Borisov, G.; Ivanova, A. |
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Affiliation: |
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AA(Institute of Astronomy, 72 Tsarigradsko chaussée Boulevard, Sofia, 1784 Bulgaria), AB(Max-Planck-Institut für Aeronomie, Katlenburg-Lindau, 37191, Germany), AC(Space Research Institute, Moscow Russia), AD(Institut für Weltraumforschung, Graz Austria), AE(Institute of Astronomy, 72 Tsarigradsko chaussée Boulevard, Sofia, 1784 Bulgaria), AF(Institute of Astronomy, 72 Tsarigradsko chaussée Boulevard, Sofia, 1784 Bulgaria) |
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Journal: |
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Icarus, Volume 160, Issue 2, p. 419-436. (Icarus Homepage) |
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Publication Date: |
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12/2002 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
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(c) 2002 Elsevier Science ( |
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DOI: |
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Bibliographic Code: |
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2002Icar..160..419B |
Comet C/1999 S4 was observed with
the 2m-telescopes of the Bulgarian National Observatory and Pik Terskol
Observatory, Northern Caucasus, Russia, at the time of its disintegration. Maps
of the dust brightness and color were constructed from images obtained in red
and blue continuum windows, free from cometary molecular emissions. We analyze the
dust environment of Comet C/1999 S4 (LINEAR) taking into account the observed
changes apparent in the brightness images and in plots of Afρ profiles as
function of the projected distance ρ from the nucleus. We also make use of the
syndyne-synchrone formalism and of a
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Title: |
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A McDonald Observatory Study of Comet 19P/Borrelly: Placing the Deep Space 1 Observations into a Broader Context |
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Authors: |
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Journal: |
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Icarus, Volume 160, Issue 2, p. 398-418. (Icarus Homepage) |
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Publication Date: |
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12/2002 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
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(c) 2002 Elsevier Science ( |
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DOI: |
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Bibliographic Code: |
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2002Icar..160..398F |
We present imaging and spectroscopic data on Comet 19P/Borrelly that were obtained around the time of the Deep Space 1 encounter and in subsequent months. In the four months after perihelion, the comet showed a strong primary (sunward) jet that is aligned with the nucleus' spin axis. A weaker secondary jet on the opposite hemisphere appeared to become active around the end of 2001, when the primary jet was shutting down. We investigated the gas and dust distributions in the coma, which exhibited strong asymmetries in the sunward/antisunward direction. A comparison of the CN and C2 distributions from 2001 and 1994 (during times when the viewing geometry was almost identical) shows that each species is remarkably similar, indicating that the comet's activity is essentially repeatable from one apparition to the next. We also measured the dust reflectivities as a function of wavelength and position in the coma, and though the dust was very red overall, we again found variations with respect to the solar direction. We used the primary jet's appearance on several dates to determine the orientation of the rotation pole to be α=214°, δ=-5°. We compared this result to published images from 1994 to conclude that the nucleus is near a state of simple rotation. However, data from the 1911, 1918, and 1925 apparitions indicate that the pole might have shifted by 5-10° since the comet was discovered. Using our pole position and the published nongravitational acceleration terms, we computed a mass of the nucleus of 3.3×1016 g and a bulk density of 0.49 g cm-3 (with a range of 0.29<ρ<0.83 g cm-3). This result is the least model-dependent comet density known to date.
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Title: |
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Long-Term Evolution of Objects in the Kuiper Belt Zone-Effects of Insolation and Radiogenic Heating |
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Authors: |
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Affiliation: |
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AA(Department of Geophysics and Planetary Sciences, Tel Aviv University, Ramat Aviv, 69978 Israel), AB(Department of Geophysics and Planetary Sciences, Tel Aviv University, Ramat Aviv, 69978 Israel), AC(Department of Geophysics and Planetary Sciences, Tel Aviv University, Ramat Aviv, 69978 Israel), AD(Department of Geophysics and Planetary Sciences, Tel Aviv University, Ramat Aviv, 69978, Israel) |
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Journal: |
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Icarus, Volume 160, Issue 2, p. 300-312. (Icarus Homepage) |
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Publication Date: |
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12/2002 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
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(c) 2002 Elsevier Science ( |
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DOI: |
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Bibliographic Code: |
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2002Icar..160..300C |
The Kuiper Belt zone is unique insofar as the major heat sources of objects a few tens of kilometers in size-solar radiation on the one hand and radioactive decay on the other-have comparable power. This leads to unique evolutionary patterns, with heat waves propagating inward from the irradiated surface and outward from the radioactively heated interior. A major radioactive source that is considered in this study is 26Al. The long-term evolution of several models with characteristics typical of Kuiper Belt objects is followed by means of a 1-D numerical code that solves the heat and mass balance equations on a spherically symmetric grid. The free parameters considered are radius (10-500 km), heliocentric distance (30-120 AU), and initial 26Al content (0-5×10-8 by mass). The initial composition assumed is a porous mixture of ices (H2O, CO, and CO2) and dust. Gases released in the interior are allowed to escape to the surface. It is shown that, depending on parameters, the interior may reach quite high temperatures (up to 180 K). The models suggest that Kuiper Belt objects are likely to lose the ices of very volatile species during early evolution; ices of less volatile species are retained in a surface layer, about 1 km thick. The models indicate that the amorphous ice crystallizes in the interior, and hence some objects may also lose part of the volatiles trapped in amorphous ice. Generally, the outer layers are far less affected than the inner part, resulting in a stratified composition and altered porosity distribution. These changes in structure and composition should have significant consequences for the short-period comets, which are believed to be descendants of Kuiper Belt objects.
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Title: |
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Spectrophotometry of the comets C/2000 WM1 (LINEAR) and C/2002 C1 (IkeyaZhang) |
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Authors: |
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Affiliation: |
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AA(State Observatory, |
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Journal: |
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Bulletin of the Astronomical Society of India, vol. 30, p.943-950 (BASI Homepage) |
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Publication Date: |
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12/2002 |
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Origin: |
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BASI |
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Keywords: |
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Comet spectrophotometry, column densities and production rates |
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Bibliographic Code: |
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2002BASI...30..943S |
Spectrophotometric observations of the coma of the comets C/2000 WM1 (LINEAR) and C/ 2002 C1 (Ikeya-Zhang) were taken during Nov, Dec 2001 and Mar, Apr 2002 respectively with 104-cm telescope of the State Observatory, Nainital. CN (3883) and C2 swan bands (4695, 5165 and 5538) have been identified in both the comets. Na I emission was detected in comet Ikeya-Zhang. An estimate of CN and C2 abundances and their production rates have been derived. Dust production rates have also been determined.
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Title: |
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Fragmentation Origin of Major Sungrazing Comets C/1970 K1, C/1880 C1, and C/1843 D1 |
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Authors: |
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Affiliation: |
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AA(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109; zs@sek.jpl.nasa.gov, ), AB(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109; zs@sek.jpl.nasa.gov, ) |
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Journal: |
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The Astrophysical Journal, Volume 581, Issue 2, pp. 1389-1398. (ApJ Homepage) |
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Publication Date: |
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12/2002 |
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Origin: |
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UCP |
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ApJ Keywords: |
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Comets: General, Comets: Individual: Alphanumeric: X/1106 C1, comets: individual (C/1843 D1, C/1880 C1), Comets: Individual: Alphanumeric: C/1882 R1, Comets: Individual: Alphanumeric: C/1887 B1, Comets: Individual: Alphanumeric: C/1945 X1, Comets: Individual: Alphanumeric: C/1963 R1, Comets: Individual: Alphanumeric: C/1965 S1, Comets: Individual: Alphanumeric: C/1970 K1, Comets: Individual: Alphanumeric: D/1993 F2, Methods: Data Analysis |
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Abstract Copyright: |
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(c) 2002: The American Astronomical Society |
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DOI: |
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Bibliographic Code: |
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2002ApJ...581.1389S |
Following our recent successful modeling of the common origin of two of the brightest members of the Kreutz system of sungrazing comets, we now examine three other objects: C/1970 K1 (White-Ortiz-Bolelli), the most recent sungrazer discovered from Earth, C/1880 C1 (Great Southern Comet), and C/1843 D1 (Great March Comet). For White-Ortiz-Bolelli, five possible origin and orbit evolution scenarios are explored. We find that its parent was neither C/1965 S1 (Ikeya-Seki), nor C/1882 R1 (Great September Comet), nor the comet of 1106 (the presumed parent of Ikeya-Seki and the 1882 comet). The motion of C/1970 K1 is consistent with a scenario in which the parent was an unknown fragment that separated from the 1106 comet at the same time as, or shortly before, Ikeya-Seki and passed through perihelion in 1970 June-July, shortly after White-Ortiz-Bolelli. The separation of White-Ortiz-Bolelli from this fragment is found to have occurred around the mid-eighteenth century, at a heliocentric distance of about 150 AU, with a relative velocity of 3-5 m s-1 in the general direction of the Sun and to the north of the orbital plane. On the other hand, we conclude that the 1880 comet separated directly from C/1843 D1, the second brightest known sungrazer, some 100-150 days after the 1843 comet's previous perihelion passage in the eleventh century, at 2.5-3 AU from the Sun, with a relative velocity of slightly more than 7 m s-1 in the generally antisolar direction and to the south of the orbital plane. The pattern of fragmentation of the Kreutz system's members discovered from Earth begins to resemble the evolution of the system's minor fragments detected coronagraphically from aboard the SOHO spacecraft, and there is significant qualitative similarity with fragmentation of comet D/1993 F2 (Shoemaker-Levy 9).
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Title: |
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Measurements of [C I] Emission from Comet Hale-Bopp |
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Authors: |
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Oliversen, R. J.; Doane, N.; Scherb, F.; Harris, W. M.; Morgenthaler, J. P. |
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Affiliation: |
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AA(NASA Goddard Space Flight Center, Greenbelt, MD 20771; ron@midnight.gsfc.nasa.gov.; Visiting Astronomer at the National Solar Observatory, operated by the Association for Research in Astronomy, under contract to the National Science Foundation.), AB(Visiting Astronomer at the National Solar Observatory, operated by the Association for Research in Astronomy, under contract to the National Science Foundation.; NASA Goddard Space Flight Center, Greenbelt, MD 20771.; Currently at Department of Astronomy, University of Wisconsin, Madison, WI 53706; doane@astro.wisc.edu.), AC(Visiting Astronomer at the National Solar Observatory, operated by the Association for Research in Astronomy, under contract to the National Science Foundation.; Department of Physics, University of Wisconsin, Madison, WI 53706; scherb@physics.wisc.edu, jpmorgen@alum.mit.edu.), AD(Space Astronomy Lab, University of Wisconsin, Madison, WI 53706; wharris@sal.wisc.edu.), AE(Department of Physics, University of Wisconsin, Madison, WI 53706; scherb@physics.wisc.edu, jpmorgen@alum.mit.edu.) |
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Journal: |
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The Astrophysical Journal, Volume 581, Issue 1, pp. 770-775. (ApJ Homepage) |
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Publication Date: |
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12/2002 |
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Origin: |
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UCP |
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ApJ Keywords: |
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Comets: Individual: Name: Hale-Bopp (C/1995 O1) |
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Abstract Copyright: |
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(c) 2002: The American Astronomical Society |
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DOI: |
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Bibliographic Code: |
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2002ApJ...581..770O |
We present quantitative
measurements of cometary [C I] 9850 Å emission obtained during observations of
comet Hale-Bopp (C/1995 O1) in 1997 March and April. The observations were
carried out using a high-resolution (λ/Δλ~40,000) Fabry-Pérot/CCD spectrometer
at the McMath-Pierce Solar telescope on
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Title: |
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Common Origin of Two Major Sungrazing Comets |
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Authors: |
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Affiliation: |
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AA(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109; zs@sek.jpl.nasa.gov, ), AB(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109; zs@sek.jpl.nasa.gov, ) |
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Journal: |
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The Astrophysical Journal, Volume 581, Issue 1, pp. 760-769. (ApJ Homepage) |
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Publication Date: |
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12/2002 |
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Origin: |
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UCP |
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ApJ Keywords: |
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Celestial Mechanics, Comets: General, Comets: Individual: Alphanumeric: X/1106 C1, comets: individual (C/1882 R1, C/1965 S1), Comets: Individual: Alphanumeric: D/1993 F2, Methods: Numerical |
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Abstract Copyright: |
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(c) 2002: The American Astronomical Society |
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DOI: |
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Bibliographic Code: |
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2002ApJ...581..760S |
Our extensive orbital calculations show that the motion of comet C/1965 S1 (Ikeya-Seki), a major member of the Kreutz sungrazing system, can be derived from the motion of its ``sister'' comet C/1882 R1 (Great September Comet) on the assumption that the two objects are fragments of a common parent that split in the year 1106, at the time when a very bright comet appeared near the Sun according to a number of historical records. Specifically, the orbit of Ikeya-Seki derived from astrometric positions in 1965-1966 is matched with remarkably high accuracy, well within the errors of observation, by (1) integrating the motion of comet C/1882 R1 back to 1106; (2) launching from the parent a fragment some 18 days after perihelion, 0.75 AU from the Sun, with a relative velocity of about 7 m s-1 nearly in the antisolar direction; and (3) integrating the fragment's motion forward to 1965. We find that having the break-up closer to the Sun or before perihelion yields grossly inferior solutions. We conclude that the fragmentation event itself was not tidal in nature, but appears to have been due to rotational, and possibly other, forces acting on the parent comet, afflicted with cracks and fissures caused by the Sun's tidal forces a few weeks earlier. We note that the derived separation velocity is in the range established for nontidal fragmentation of minor sungrazers at large heliocentric distances and that there are obvious similarities with the behavior of comet D/1993 F2 (Shoemaker-Levy 9) following its close encounter with Jupiter in 1992 July.
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Title: |
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The Origin of the Solar Wind |
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Authors: |
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Journal: |
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American Scientist, vol. 90, Issue 6, p.532 |
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Publication Date: |
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12/2002 |
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Origin: |
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WEB |
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Bibliographic Code: |
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2002AmSci..90..532W |
Nearly 1,400 years ago, Chinese astronomers noticed that comet tails always point away from the Sun. They concluded that the Sun must have <em>chi</em>—a basic life force—that blows the tails away. It wasn't until the middle of the 20th century that scientists understood that this "force" actually consisted of little pieces of the sun itself—protons and electrons—blowing out into the solar system as a "wind" at more than a million kilometers per hour. The traditional view of the solar wind's origins suggests that it originates from special regions on the Sun, called coronal holes. Woo and Habbal present new evidence showing that the wind actually emanates from all regions on the Sun.
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Title: |
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Production, processing and characterisation techniques for cosmic dust analogues |
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Authors: |
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Rotundi, A.; Brucato, J. R.; Colangeli, L.; Ferrini, G.; Mennella, V.; Palomba, E.; Palumbo, P. |
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Affiliation: |
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AA(Ist. di
Mat., Fis. e Appl., Università "Parthenope", Via A. De Gasperi 5,
I-80133 Napoli, Italy; rotundi@uninav.it) |
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Journal: |
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Meteoritics & Planetary Science, vol. 37, no. 11, pp. 1623-1635 (2002) |
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Publication Date: |
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11/2002 |
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Origin: |
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M&PS |
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Bibliographic Code: |
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2002M&PS...37.1623R |
The laboratory analyses of cosmic dust analogues, that in the context of this paper include interstellar, circumstellar as well as cometary dust, have a critical role in the study of circumstellar and cometary dust. The morphological, structural and chemical characterisation of these analogues are critical for comparisons of their IR and UV spectra with those obtained by astronomical observations, as well as for modelling purposes. Besides, the results from these laboratory studies are important to the success of space missions to comets when testing and calibrating the payload instruments. The interpretations of returned scientific data would benefit from the comparison with data recorded by the instruments in a laboratory setting for different classes of previously characterised analogues. We produced various types of condensed samples: (1) Mg,Fe-silicates, (olivine; pyroxene), (2) carbon-rich dust and (3) mixed carbon-silicate dust. The samples were prepared using different techniques, viz. (1) laser bombardment of solid targets in an Ar and O2 atmosphere, (2) arc discharge in an Ar and H2 atmosphere, and (3) grinding powders of natural minerals. We simulated various post-condensation processes, such as thermal annealing, UV irradiation, ion bombardment and exposure to atomic hydrogen. These processes produced compound samples of a wide range of physico-chemical properties. To identify their textures, morphologies, grain compositions and crystallographic properties we used electron microscopy and far-ultraviolet to far-infrared (millimiter range) spectroscopy.
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Title: |
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Low-energy helium ion irradiation-induced amorphization and chemical changes in olivine: Insights for silicate dust evolution in the interstellar medium |
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Authors: |
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Carrez, Philippe; Demyk, Karine; Cordier, Patrick; Gengembre, Léon; Grimblot, Jean; D'Hendecourt, Louis; Jones, Anthony P.; Leroux, Hugues |
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Affiliation: |
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AA(Laboratoire
de Structure et Propriétés de l'Etat Solide (ESA CNRS 8008)-Bât. C6,
Université des Sciences et Technologies de Lille, 59655 Villeneuve
d'Ascq-Cedex, |
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Journal: |
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Meteoritics & Planetary Science, vol. 37, no. 11, pp. 1599-1614 (2002) |
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Publication Date: |
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11/2002 |
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Origin: |
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M&PS |
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Bibliographic Code: |
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2002M&PS...37.1599C |
We present the results of irradiation experiments aimed at understanding the structural and chemical evolution of silicate grains in the interstellar medium (ISM). A series of He+ irradiation experiments have been performed on ultra-thin olivine, (Mg,Fe)2SiO4, samples having a high surface/volume (S/V) ratio, comparable to the expected S/V ratio of interstellar dust. The energies and fluences of the helium ions used in this study have been chosen to simulate the irradiation of interstellar dust grains in supernovae shock waves. The samples were mainly studied using Analytical Transmission Electron Microscopy (ATEM). Our results show that olivine is amorphized by low-energy ion irradiation. Changes in composition are also observed. In particular, irradiation leads to a decrease of the atomic ratios O/Si and Mg/Si as determined by X-ray Photoelectron Spectroscopy (XPS) and by X-ray Energy Dispersive Spectroscopy (EDS). This chemical evolution is due to the differential sputtering of atoms near the surfaces. We also observe a reduction process resulting in the formation of metallic iron. The use of very thin samples emphasizes the role of surface/volume ratio and thus the importance of the particle size in the irradiation-induced effects. These results allow us to account qualitatively for the observed properties of interstellar grains in different environments, i.e., at different stages of their evolution : chemical and structural evolution in the interstellar medium, from olivine to pyroxene-type and from crystalline to amorphous silicates, porosity of cometary grains as well as the formation of metallic inclusions in silicates.
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Title: |
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Condensation processes in astrophysical environments: The composition and structure of cometary grains |
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Authors: |
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Nuth, Joseph A., III; Rietmeijer, Frans J. M.; Hill, Hugh G. M. |
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Affiliation: |
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AA(Astrochemistry Branch, Code 691, NASA's Goddard Space Flight Center, Greenbelt, Maryland 20771, USA; nuth@gsfc.nasa.gov) |
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Journal: |
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Meteoritics & Planetary Science, vol. 37, no. 11, pp. 1579-1590 (2002) |
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Publication Date: |
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11/2002 |
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Origin: |
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M&PS |
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Bibliographic Code: |
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2002M&PS...37.1579N |
We review the results of our recent experimental studies of astrophysical dust analogs. We discuss the condensation of amorphous silicates from mixed metal vapors, including evidence that such condensates form with metastable eutectic compositions. We consider the spectral evolution of amorphous magnesium silicate condensates as a function of time and temperature. Magnesium silicate smokes anneal readily at temperatures of ~1000-1100 K. In contrast we find that iron silicates require much higher temperatures (~1300 K) to bring about similar changes on the same timescale (days to months). We first apply these results to ISO observations of crystalline magnesium silicate grains around high-mass-outflow AGB stars in order to demonstrate their general utility in a rather simple environment. Finally, we apply these experimental results to infrared observations of comets and protostars in order to derive some interesting conclusions regarding large-scale nebular dynamics, the natural production of organic molecules in protostellar nebulae and the use of crystalline magnesium silicates as a relative indicator of a comet's formation age.
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Title: |
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Hydrogen cyanide in comet C/1996 B2 Hyakutake |
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Authors: |
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Magee-Sauer, Karen; Mumma, Michael J.; DiSanti, Michael A.; Dello Russo, Neil |
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Journal: |
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Journal of Geophysical Research (Planets), Volume 107, Issue E11, pp. 6-1, CiteID 5096, DOI 10.1029/2002JE001863 (JGRE Homepage) |
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Publication Date: |
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11/2002 |
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Origin: |
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AGU |
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AGU Keywords: |
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Planetology: Solar System Objects: Comets, Planetology: Comets and Small Bodies: Composition, Planetology: Comets and Small Bodies: Atmospheres-composition and chemistry, |
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Abstract Copyright: |
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(c) 2002: American Geophysical |
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DOI: |
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Bibliographic Code: |
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2002JGRE.107k....6M |
Spectral emission from HCN in C/1996 B2 Hyakutake was detected on UT 1996 March 24.4 (rh = 1.06 AU, Δ = 0.106 AU), using the CSHELL infrared spectrometer at the NASA Infrared Telescope Facility. A Boltzmann analysis of eight ro-vibrational lines in the ν3 band returned a rotational temperature (83 +/- 9 K) for a region centered on the nucleus. The global HCN production rate was (4.50 +/- 0.81) × 1026 molecules s-1. The HCN abundance relative to water is then (0.18 +/- 0.04)%, based on direct measurements of H2O made on the same night with the same instrument and reduced with the same data processing algorithms. The measured spatial distribution for HCN is consistent with its release at the nucleus; no significant contribution from a distributed source is required within ~600 km of the nucleus. We use these data to obtain insights regarding the origin of HCN in this comet.
|
Title: |
|
Production of ethane and water in comet C/1996 B2 Hyakutake |
|
Authors: |
|
Dello Russo, Neil Dello; Mumma, Michael J.; DiSanti, Michael A.; Magee-Sauer, Karen |
|
Journal: |
|
Journal of Geophysical Research (Planets), Volume 107, Issue E11, pp. 5-1, CiteID 5095, DOI 10.1029/2001JE001838 (JGRE Homepage) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
AGU |
|
AGU Keywords: |
|
Planetology: Comets and Small Bodies: Atmospheres-composition and chemistry, Planetology: Comets and Small Bodies: Composition, Planetology: Comets and Small Bodies: Ice, Planetology: Comets and Small Bodies: Radiation and spectra, |
|
Abstract Copyright: |
|
(c) 2002: American Geophysical |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002JGRE.107k....5D |
Ethane (C2H6) and water (H2O) were detected in Comet C/1996 B2 Hyakutake between UT 1996 March 23.4 (Rh = 1.08 AU preperihelion) and 1996 April 12.2 (Rh = 0.64 AU preperihelion). Our long-slit infrared spectra featured both high spectral dispersion and high spatial resolution about the nucleus, permitting the extraction of rotational temperatures, production rates, and spatial distributions of species along the slit. Production rates were measured for water (on four dates) and ethane (on three dates). Their average relative abundance was C2H6/H2O = (6.2 +/- 0.7) × 10-3. The spatial distributions of C2H6 and H2O molecules in the coma were consistent with both species being released directly from the nucleus on all dates, although asymmetries about the nucleus are seen for both gas and dust.
|
Title: |
|
Experimental levitation of dust grains in a plasma sheath |
|
Authors: |
|
Sickafoose, A. A.; Colwell, J. E.; Horányi, M.; Robertson, S. |
|
Journal: |
|
Journal of Geophysical Research (Space Physics), Volume 107, Issue A11, pp. SMP 37-1, CiteID 1408, DOI 10.1029/2002JA009347 (JGRA Homepage) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
AGU |
|
AGU Keywords: |
|
Space Plasma Physics: Laboratory studies, Space Plasma Physics: Experimental and mathematical techniques, Planetology: Solar System Objects: Dust, Planetology: Comets and Small Bodies: Dust, |
|
Abstract Copyright: |
|
(c) 2002: American Geophysical |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002JGRA.107kSMP37S |
Dust grains have been observed to levitate above the surface of the Moon and as spokes in Saturn's rings. In order to gain a better understanding of these observations, we have performed levitation experiments on dust grains in a low-density plasma. Plasma sheath potential profiles, measured by an emissive probe, are used to determine the spatial dependence of the electric force on a grain in the sheath. The observed levitation height agrees with the values calculated using orbital-motion-limited charging theory and force balance equations. Levitating grains were also exposed to an ultraviolet light source to induce photoemission. Three types of dust were investigated: polystyrene divinylbenzene microspheres 10.0 +/- 0.5 μm in diameter, glass microballoons <38 μm in diameter, and JSC-1 (lunar regolith simulant) <25 μm in diameter. Our experimental results show that (1) various types and sizes of grains can levitate in a plasma sheath above a conducting surface; (2) levitating grains of a standard size float at a height corresponding to that predicted by theory; (3) exposure to UV light causes the grain levitation height to decrease slightly as a result of less negative charge; and (4) a mechanism to inject grains into the sheath is not necessary if the electric field is sufficiently strong.
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Title: |
|
Is the D/H Ratio in the Comet Coma Equal to the D/H Ratio in the Comet Nucleus? |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Department of Geophysics and Planetary Sciences, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv Israel), AB(Department of Geophysics and Planetary Sciences, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv Israel), AC(Department of Geophysics and Planetary Sciences, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv Israel) |
|
Journal: |
|
Icarus, Volume 160, Issue 1, p. 208-211. (Icarus Homepage) |
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Publication Date: |
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11/2002 |
|
Origin: |
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ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science ( |
|
DOI: |
|
|
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Bibliographic Code: |
|
2002Icar..160..208P |
We present a simple, semianalytic model of the vaporization of H2O and HDO ice from a comet nucleus. We use this model to show that the flux of HDO relative to H2O can be much higher, at times, than would be expected from the D/H ratio in the nuclear ice itself. This effect varies with position in the comet's orbit. It is negligible sufficiently near the Sun but could lead to erroneous interpretations of the primordial D/H ratio in cometary ice if measurements are made in other parts of the cometary orbit.
|
Title: |
|
New Activity of Chiron: Results from 5 Years of Photometric Monitoring |
|
Authors: |
|
Duffard, René; Lazzaro, Daniela; Pinto, Sandro; Carvano, Jorge; Angeli, Claudia; Alvarez-Candal, Alvaro; Fernández, Silvia |
|
Affiliation: |
|
AA(Observatório
Nacional, Coordenação de Astronomía e Astrofísica, Rio de Janeiro, 20921-400,
Brazil), AB(Observatório Nacional, Coordenação de Astronomía e Astrofísica,
Rio de Janeiro, 20921-400 Brazil), AC(Observatório Nacional, Coordenação de
Astronomía e Astrofísica, Rio de Janeiro, 20921-400 Brazil), AD(Observatório
Nacional, Coordenação de Astronomía e Astrofísica, Rio de Janeiro, 20921-400
Brazil), AE(Observatório Nacional, Coordenação de Astronomía e Astrofísica,
Rio de Janeiro, 20921-400 Brazil), AF(Facultad de Matemática, Astronomía y
Física, Universidad Nacional de Córdoba, Córdoba, 5000 Argentina),
AG(Observatorio Astronómico, Universidad Nacional de Córdoba, Laprida 854,
Córdoba, 5000 Argentina) |
|
Journal: |
|
Icarus, Volume 160, Issue 1, p. 44-51. (Icarus Homepage) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science ( |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002Icar..160...44D |
The results of photometric observations of Centaur object Chiron carried out at the Observatório do Pico dos Dias (OPD, Brazil), the Estación Astrofísica de Bosque Alegre (EABA, Argentina), and Complejo Astronómico El Leoncito (CASLEO, Argentina) from 1997 to 2001 are presented here. The analysis of the photometric data shows that the brightness of Chiron reached a minimum value in 1999 and began increasing again in 2000. The absolute magnitude, HV, varied from 7.26 in June 1999 to 5.78 in April 2001. The data tend to indicate that Chiron is starting a new outburst of activity which is compatible with a sporadic cometary behavior not related to heliocentric distance.
|
Title: |
|
The Jovian Stratosphere after Comet Shoemaker-Levy/9: Unusual Isotopic Ratios in Molecular Trace Constituents |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Joint Astronomy Centre, 660 North A'ohōkū Place, Hilo, HI 96720; ), AB(LESIA, Observatoire de Paris, 5 Place Jules Janssen, F-92195 Meudon, France), AC(Institut de Radio Astronomie Millimétrique, 300 Rue de la Piscine, F-38406 Saint Martin d'Hères, France), AD(Institute for Astronomy, 2680 Woodlawn Drive, University of Hawaii at Manoa, Honolulu, HI 96822) |
|
Journal: |
|
The Astrophysical Journal, Volume 580, Issue 1, pp. 598-605. (ApJ Homepage) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
UCP |
|
ApJ Keywords: |
|
Comets: Individual: Name: Shoemaker-Levy/9, Planets and Satellites: Individual: Jupiter, Submillimeter |
|
Abstract Copyright: |
|
(c) 2002: The American Astronomical Society |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002ApJ...580..598M |
Since the collision of comet Shoemaker-Levy/9 with Jupiter in 1994 July, a number of minor molecular species have been observed to persist in the stratosphere of the planet. Here we report observations acquired in 1998 September at frequencies near 350 GHz (wavelength 850 μm) of HCN and CS and their respective isotopomers H13CN, HC15N, and C34S. Through radiative transfer modeling of the observed lines, we find that the isotopic abundance ratios 12C/13C, 14N/15N, and 32S/34S are considerably elevated with respect to their terrestrial values. We speculate that this result indicates an unusual composition for comet Shoemaker-Levy/9, or that cometary grains evaporated in the collisions significantly modified the isotope ratios.
|
Title: |
|
Grain Properties of Comet C/1995 O1 (Hale-Bopp) |
|
Authors: |
|
Harker, David E.; Wooden, Diane H.; Woodward, Charles E.; Lisse, Carey M. |
|
Affiliation: |
|
AA(NASA Ames Research Center, Space Science Division, MS 245-3, Moffet Field, CA 94035-1000; National Research Council Associate.; Visiting Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under contract with the National Aeronautics and Space Administration.), AB(NASA Ames Research Center, Space Science Division, MS 245-3, Moffet Field, CA 94035-1000), AC(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455), AD(Department of Astronomy, University of Maryland, College Park, MD 20742) |
|
Journal: |
|
The Astrophysical Journal, Volume 580, Issue 1, pp. 579-597. (ApJ Homepage) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
UCP |
|
ApJ Keywords: |
|
Comets: General, comets: individual (C/1995 O1 Hale-Bopp), Infrared: Solar System |
|
Abstract Copyright: |
|
(c) 2002: The American Astronomical Society |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002ApJ...580..579H |
We present the analysis of 7.6-13.2 μm infrared (IR) spectrophotometry (R~=250) of comet C/1995 O1 (Hale-Bopp), in conjunction with concurrent observations that extend the wavelength coverage of the spectral energy distribution from near- to far-infrared wavelengths. The observations include temporal epochs preperihelion (1996 October and 1997 February UT), near perihelion (1997 April UT), and postperihelion (1997 June UT). Through the modeling of the thermal emission from small, amorphous carbon grains and crystalline and amorphous silicate grains in Hale-Bopp's coma, we find that as the comet approached perihelion, the grain size distribution (the Hanner modified power law) steepened (from N=3.4 preperihelion to N=3.7 near and postperihelion), along with an increase in the fractal porosity of larger (greater than 1 μm) grains. The peak of the grain size distribution remained constant (ap=0.2 μm) at each epoch. We attribute the emergence of the 9.3 μm peak near perihelion to crystalline orthopyroxene grains released during epochs of high jet activity. Crystalline silicates (olivine and orthopyroxene) make up about 30% (by mass) of the submicron-sized (<=1 μm) dust grains in Hale-Bopp's coma during each epoch.
|
Title: |
|
Laboratory study of annealed amorphous MgSiO3 silicate using IR spectroscopy and synchrotron X-ray diffraction |
|
Authors: |
|
Thompson, S. P.; Fonti, S.; Verrienti, C.; Blanco, A.; Orofino, V.; Tang, C. C. |
|
Affiliation: |
|
AA(Daresbury
Laboratory, Warrington, Cheshire WA4 4AD, Great Britain), AB(Dipartimento di
Fisica, Universita di Lecce, C. P. 193 - Via Arnesano, 73100 Lecce, Italy),
AC(Dipartimento di Fisica, Universita di Lecce, C. P. 193 - Via Arnesano,
73100 Lecce, Italy), AD(Dipartimento di Fisica, Universita di Lecce, C. P.
193 - Via Arnesano, 73100 Lecce, Italy), AE(Dipartimento di Fisica,
Universita di Lecce, C. P. 193 - Via Arnesano, 73100 Lecce, Italy),
AF(Daresbury Laboratory, Warrington, Cheshire WA4 4AD, Great Britain) |
|
Journal: |
|
Astronomy and Astrophysics, v.395, p.705-717 (2002) (A&A Homepage) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
A&A |
|
A&A Keywords: |
|
methods: laboratory, comets: general, stars: circumstellar matter |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002A&A...395..705T |
We present the results of combining in situ high resolution synchrotron X-ray powder diffraction and infrared spectroscopic measurements on an amorphous pyroxene powder sample annealed in the region of 1000 K. We find using both techniques that the crystalline structure formed during annealing is Mg2SiO4 (forsterite), but that the presence of certain features in the 10 mu m band normally attributed to crystalline enstatite (MgSiO3) is contradicted by spectroscopy in the 20 mu m region (along with certain other 10 mu m band features) and X-ray diffraction. Both indicate crystalline forsterite as the only crystalline phase formed at this temperature. We discuss the possible mechanism of forsterite formation from amorphous pyroxene and identify the presence of proto-forsteritic structures in the amorphous starting material. We suggest the likely origin of the 10 mu m band ``crystalline enstatite'' features as being due to short-range improvements in the amorphous MgSiO3 network ordering which are not necessarily accompanied by the formation of crystalline enstatite structure. These results not only suggest that the formation of crystalline enstatite dust grains via annealing may be difficult to realise at this temperature, but also highlight the possibility, in the absence of additional corroborating evidence, of misidentifying the nature of the carrier of the 10 mu m ``enstatite'' features when observed in the spectra of objects such as comets. We also discuss the evolution of fine structure in the region of 15 to 16 mu m, which may serve as an observational indicator of grain processing in stellar sources.
|
Title: |
|
On the origin of comet C/1999 S4 LINEAR |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Universidad Complutense de Madrid, |
|
Journal: |
|
Astronomy and Astrophysics, v.395, p.697-704 (2002) (A&A Homepage) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
A&A |
|
A&A Keywords: |
|
minor planets, asteroids, comets: general, comets: individual: C/1994 S4 LINEAR, Kuiper belt, Oort cloud, solar system: formation |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002A&A...395..697D |
Current models of the formation of
comets in the Solar System assume that the most likely formation site for these
pristine objects is in the Uranus-Neptune zone or just beyond with subsequent
dynamical ejection by the growing protoplanets to distant orbits to form the Oort
cloud. However, the composition of the recently disintegrated comet C/1999 S4
LINEAR suggests that it was most likely formed in the Jupiter-Saturn region
(Mumma et al. 2001b; Kawakita et al. 2001). In this paper we argue that
cometesimals could easily appear inside exterior resonances resulting from gas
drag, between the orbits of Jupiter and Saturn and beyond Saturn, during the
formation of these giant planets. Then, the trapped material could evolve into
actual comets by means of collisional coagulation, followed by gravitational
instability of a layer of macroscopic bodies or two-body accretion. Properties
of these objects would be rather different from those found in classical comets
formed beyond
|
Title: |
|
Deuterium in comets-and AGB stars? |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Space Science Division, MS 245-3, |
|
Journal: |
|
Planetary and Space Science, Volume 50, Issue 12-13, p. 1215-1219. (P&SS Homepage) |
|
Publication Date: |
|
10/2002 |
|
Origin: |
|
ELSEVIER |
|
Bibliographic Code: |
|
2002P&SS...50.1215R |
We discuss the deuterium chemistry of cometary comae, and show how the fractionation observed in coma molecules relates to the D/H ratios in the nuclear ices. For most molecules, we find that the fractionation is unchanged in the coma. In addition, we calculate the potential effects of degradation of D-rich polymers/organic refractory material on selected gas-phase fractionation ratios. We demonstrate that for molecules known to have an extended coma source, the observed D/H ratios may not necessarily reflect those in the nuclear ice. The recent detection of water vapour in the stellar wind of the carbon-rich red giant /IRC+10°216 has been attributed to the vaporization of a remnant population of comets surrounding this evolved star. This theory would be confirmed by the detection of deuterated molecules in this object: as deuterium is destroyed in stars, any D-bearing molecules must originate from cometary or planetary objects. We quantitatively assess the possibility of detecting HDO in this source if such comets contain similar D/H ratios to those in our solar system, and show that the 111-000 transition at 894GHz is the most promising candidate for detection.
|
Title: |
|
The magnitude distribution and evolution of short-period comets |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Department of Physics and Astronomy, The University, |
|
Journal: |
|
Monthly Notice of the Royal Astronomical Society, Volume 336, Issue 2, pp. 363-372. (MNRAS Homepage) |
|
Publication Date: |
|
10/2002 |
|
Origin: |
|
MNRAS |
|
MNRAS Keywords: |
|
comets: general |
|
Abstract Copyright: |
|
(c) RAS |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002MNRAS.336..363H |
The magnitude distribution, perihelion distribution, nucleus size variation and evolution of the short-period comet population are re-assessed. Short-period comets with perihelion distances greater than 2 au have a magnitude distribution index of about 2.3, similar to that of the long-period comets. This index progressively increases for smaller perihelion distances, owing to the pronounced effects of cometary decay. The relationship between absolute magnitude and nucleus radius is investigated, as is the relationship between cometary decay rate and perihelion distance. It is estimated that 50 per cent of the known short-period comets will decay away completely in the next 2600 yr, a further 25 per cent going in the following 2300 yr.
|
Title: |
|
Variations of physical parameters in the plasma tail of comet Abe (C/1970 N1) and their connection with solar activity |
|
Authors: |
|
Shabas, N. L.; Churyumov, K. I.; Luk'yanyk, I. V.; Kravtsov, F. I. |
|
Journal: |
|
Kinematika i
Fizika Nebesnykh Tel, vol. 18, no. 5, p. 433-440. |
|
Publication Date: |
|
10/2002 |
|
Origin: |
|
KFNT |
|
Language: |
|
Russian |
|
Bibliographic Code: |
|
2002KFNT...18..433S |
More exact estimates of physical parameters in the plasma tail of comet Abe (C/1970 N1) are presented for 24 dates. The diffusion model was used. The connection between the changes of the magnetic field in the plasma tail of the comet in the period from 1970 September 30 to October 8 and in solar flares is investigated.
|
Title: |
|
Scaling of hypervelocity impact craters in ice with impact angle |
|
Authors: |
|
|
|
Journal: |
|
Journal of Geophysical Research (Planets), Volume 107, Issue E10, pp. 6-1, CiteID 5076, DOI 10.1029/2001JE001525 (JGRE Homepage) |
|
Publication Date: |
|
10/2002 |
|
Origin: |
|
AGU |
|
AGU Keywords: |
|
Planetology: Comets and Small Bodies: Ice, Planetology: Comets and Small Bodies: Impact phenomena, Planetology: Comets and Small Bodies: Surfaces and interiors, Planetology: Comets and Small Bodies: Satellites, Planetology: Solar System Objects: Comets, |
|
Abstract Copyright: |
|
(c) 2002: American Geophysical |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002JGRE.107j....6G |
Hypervelocity oblique impacts using spherical 1 mm diameter aluminum projectiles at velocities of (5.2 +/- 0.2) km s-1 were incident at angles ranging from normal (0° to the vertical) to grazing incidence (80°) onto thick polycrystalline H2O ice targets at 253 K. Data were obtained to distinguish changes in crater size and shape. The resultant craters had a deep central pit surrounded by a shallower terrace. Results on crater size showed that volume and crater depth had varying levels of dependence on obliquity for the full angular range, and terrace depth had a dependence only at angles > 45°. Length and width measurements held a strong dependence on obliquity only at angles > 50° from the normal. These results for ice show that it is hard to determine angle of impact from crater morphology. Although crater depth and volume do change with angle, it would be hard to separate this effect from the influence of an impact of a projectile of different speed, density, etc., which might also affect crater depth or crater depth/diameter ratios. Only at extreme angles > 70° do real differences in shape emerge for ice.
|
Title: |
|
Dust Grains in the Comae and Tails of Sungrazing Comets: Modeling of Their Mineralogical and Morphological Properties |
|
Authors: |
|
Kimura, Hiroshi; Mann, Ingrid; Biesecker, Douglas A.; Jessberger, Elmar K. |
|
Affiliation: |
|
AA(Institut für Planetologie, Westfälische Wilhelms-Universität, Wilhelm-Klemm-Straße 10, Münster, D-48149, Germany), AB(Institut für Planetologie, Westfälische Wilhelms-Universität, Wilhelm-Klemm-Straße 10, Münster, D-48149 Germany), AC(), AD(Institut für Planetologie, Westfälische Wilhelms-Universität, Wilhelm-Klemm-Straße 10, Münster, D-48149 Germany) |
|
Journal: |
|
Icarus, Volume 159, Issue 2, p. 529-541. (Icarus Homepage) |
|
Publication Date: |
|
10/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science ( |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002Icar..159..529K |
Observations of sungrazing comets, all of which belong to the Kreutz family, provide the opportunity of studying the properties of dust in the comae and tails of the comets. On the basis of available information on cometary and interplanetary dust as well as observations of dust in the tails of sungrazers, we model dust in sungrazing comets as fluffy silicate aggregates of submicrometer sizes. To better interpret observational data, we numerically calculate the solar radiation pressure, the equilibrium temperature, and the sublimation and crystallization rates of silicate grains near the Sun. Our results show that the dust tails contain aggregates of submicrometer crystal grains, but not amorphous grains, since amorphous silicates mostly crystallize after release from the comets. The peak in the lightcurves of the dust comae observed either at 11.2 or 12.3 solar radii (Rsolar) seems to result from sublimation of fluffy aggregates consisting of crystalline or amorphous olivines, respectively. We attribute an additional enhancement in the lightcurves inside 7 Rsolar to increasing out-flow of crystalline and amorphous pyroxenes composed fluffy aggregates. According to our model, the observed lightcurves indicate a high abundance of olivine and a low abundance of pyroxene in the comets, which may bear implications about the dynamical and thermal history of the sungrazers and their progenitor.
|
Title: |
|
A comparison between the compositions of cometary and interstellar materials. I. Molecular abundances |
|
Authors: |
|
|
|
Journal: |
|
Contributions of the Astronomical Observatory Skalnaté Pleso, vol. 32, no. 2, p. 145-174. (CoSka Homepage) |
|
Publication Date: |
|
10/2002 |
|
Origin: |
|
COSKA |
|
Keywords: |
|
comets: general, Solar System: formation, ISM: clouds, ISM: molecules |
|
Bibliographic Code: |
|
2002CoSka..32..145N |
Comets were created as a by-product of planet formation from pristine interstellar material. A certain similarity between the composition of both cometary nuclei and interstellar clouds has actually be observed by several authors in few last decades. We summarize the quantitative measurements of abundances of observed molecules in both the above entities and discuss their similarities and differences. The found variety of the chemical composition of comets is practically within the range of observed molecular composition of relatively cold matter in the Galaxy. It proves that the gaseous and dusty components from which the cometary nuclei were built are primordial.
|
Title: |
|
Production, Outflow Velocity, and Radial Distribution of H2O and OH in the Coma of Comet C/1995 O1 (Hale-Bopp) from Wide-Field Imaging of OH |
|
Authors: |
|
Harris, Walter M.; Scherb, Frank; Mierkiewicz, Edwin; Oliversen, Ronald; Morgenthaler, Jeffrey |
|
Affiliation: |
|
AA(University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706.), AB(University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706.), AC(University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706.), AD(Goddard Space Flight Center.), AE(University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706.) |
|
Journal: |
|
The Astrophysical Journal, Volume 578, Issue 2, pp. 996-1008. (ApJ Homepage) |
|
Publication Date: |
|
10/2002 |
|
Origin: |
|
UCP |
|
ApJ Keywords: |
|
Comets: Individual: Name: Hale-Bopp 1995 O1 |
|
Abstract Copyright: |
|
(c) 2002: The American Astronomical Society |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002ApJ...578..996H |
Observations of OH are a useful proxy of the water production rate (QH2O) and outflow velocity (VH2O) in comets. From wide-field images taken on 1997 March 28 and April 8 that capture the entire scale length of the OH coma of comet C/1995 O1 (Hale-Bopp), we obtain QOH from the model-independent method of aperture summation and QH2O from the OH photochemical branching ratio, BROH. Using an adaptive ring summation algorithm, we extract the radial brightness distribution of OH 0-0 band emission out to cometocentric distances of up to 106 km, both as azimuthal averages and in quadrants covering different position angles relative to the comet-Sun line. These profiles are fitted using both fixed and variable velocity two-component spherical expansion models to estimate VOH with increasing distance from the nucleus. The OH coma of Hale-Bopp was more spatially extended than those of previous comets, and this extension is best matched by a variable acceleration of H2O and OH that acted across the entire coma, but was strongest within 1-2×104 km from the nucleus. Our models indicate that VOH at the edge of our detectable field of view (106 km) was ~2-3 times greater in Hale-Bopp than for a 1P/Halley class comet at 1 AU, which is consistent with the results of more sophisticated gas-kinetic models, extrapolation from previous observations of OH in comets with QH2O>1029s-1, and direct radio measurements of the outer coma Hale-Bopp OH velocity. The likely source of this acceleration is thermalization of the excess energy of dissociation of H2O and OH over an extended collisional coma. When the coma is broken down by quadrants in position angle, we find an azimuthal asymmetry in the radial distribution that is characterized by an increase in the spatial extent of OH in the region between the orbit-trailing and anti-Sunward directions. Model fits specific to this area and comparison with radio OH measurements suggest greater acceleration here, with VOH~1.5 times greater at a 106 km cometocentric distance than elsewhere in the coma. We discuss several mechanisms that may have acted within the coma to produce the observed effect.
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Title: |
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Observations at Nançay of the OH 18-cm lines in comets. The data base. Observations made from 1982 to 1999 |
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Authors: |
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Crovisier, J.; Colom, P.; Gérard, E.; Bockelée-Morvan, D.; Bourgois, G. |
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Affiliation: |
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AA( |
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Journal: |
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Astronomy and Astrophysics, v.393, p.1053-1064 (2002) (A&A Homepage) |
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Publication Date: |
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10/2002 |
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Origin: |
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A&A |
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A&A Keywords: |
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comets: general, radio lines: solar system, solar system: general |
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DOI: |
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Bibliographic Code: |
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2002A&A...393.1053C |
Since the apparition of comet Kohoutek 1973 XII, the 18-cm lines of the OH radical have been systematically observed in a number of comets with the Nançay radio telescope. Between 1973 and 1999, 52 comets have been successfully detected. This allowed an evaluation of the cometary water production rates and their evolution with time, as well as a study of several physical processes such as the excitation mechanisms of the OH radio lines, the expansion of cometary atmospheres, their anisotropy in relation to non-gravitational forces, and the Zeeman effect in relation to the cometary magnetic field. Part of these observations and their analysis have already been published. The bulk of the results are now organized in a data base. The present paper is a general presentation of the Nançay cometary data base and a more specific description of the observations of 53 cometary apparitions between 1982 and 1999. Comets observed before 1982 are only partly incorporated in the data base. Observations of comets since 2000 have benefited from a major upgrade of the telescope; they will be presented in forthcoming publications. Appendix A, Table 2 and figures of the sum spectra are only available in electronic form at http://www.edpsciences.org The spectra and tables of the Appendix are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-in/qcat?J/A+A/393/1053
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Title: |
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On the Light-Absorbing Surface Layer of Cometary NucleiII. Thermal Modeling |
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Authors: |
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Affiliation: |
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AA(Department of Astronomy and Space Physics, Uppsala University, Box 515, Uppsala, SE-751 20, Sweden), AB(Keldysh Institute of Applied Mathematics, Miusskaya Sq. 4, Moscow, 125047 Russia) |
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Journal: |
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Icarus, Volume 159, Issue 1, p. 239-258. (Icarus Homepage) |
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Publication Date: |
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09/2002 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
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(c) 2002 Elsevier Science ( |
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DOI: |
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Bibliographic Code: |
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2002Icar..159..239D |
The classical way to treat absorption of solar light in thermophysical modeling of cometary nuclei (and other ice-rich bodies such as jovian satellites) has been to assume complete opaqueness of the surface material. However, as shown by Davidsson and Skorov (2002, Icarus156, 223-248), substantial light penetration can occur in porous ice even if it is very dusty, implying that gradual absorption of energy in a surface layer should be accounted for. We present a thorough comparison between a surface energy absorption model and a layer energy absorption model, for various combinations of heliocentric distances, conductivities, opacities, pore sizes, and rotational periods relevant for cometary nuclei, by fully solving the coupled differential equations of heat transfer and gas diffusion. We find substantial differences between the models in terms of gas production rate, thermal lag angle, surface temperature, and the origin of coma molecules. For example, the surface energy absorption model overestimates the total gas production by a factor of 2-7, underestimates the lag angle by a factor of 2-3, and places the origin of coma molecules at the surface, instead of the near-surface interior.
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Title: |
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3- to 14-μm Spectroscopy of Comet C/1999 T1 (McNaught-Hartley) |
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Authors: |
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Journal: |
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Icarus, Volume 159, Issue 1, p. 234-238. (Icarus Homepage) |
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Publication Date: |
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09/2002 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
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(c) 2002 Elsevier Science ( |
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DOI: |
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Bibliographic Code: |
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2002Icar..159..234L |
We report spectroscopy of Comet C/1991 T1 (McNaught-Hartley) at 3-13 μm on January 31.62 and February 1.7 2001 UT (delta=1.29 AU, r=1.40 AU) using the broadband array spectrograph system on the IRTF. The spectrum showed a silicate emission feature extending about 20% above the continuum. Two emission features at 10.3 and 11.2 μm appeared above the silicate band, the latter seemingly indicative of crystalline olivine. The 10.3-μm feature is only a 1-2 sigma detection but if real could indicate the presence of hydrated silicates. The color temperature at 8-13 μm was 260+/-10 K, approximately 6% above the blackbody radiative equilibrium temperature of 235 K. The magnitude at [N] was 3.13+/-0.02. On the second night, the comet had brightened slightly ([N]=2.98+/-0.02) and the two prominent emission features were absent, although the silicate emission feature maintained its trapezoidal shape with shoulders at 9.5 and 11.2 μm.
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Title: |
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Long- and Short-Term Photometric Behavior of Comet Hyakutake (1996 B2) |
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Authors: |
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Journal: |
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Icarus, Volume 159, Issue 1, p. 210-233. (Icarus Homepage) |
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Publication Date: |
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09/2002 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
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(c) 2002 Elsevier Science ( |
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DOI: |
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Bibliographic Code: |
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2002Icar..159..210S |
Narrowband filter photometry observations of Comet Hyakutake (1996 B2) were used to investigate this comet's short-term variability as well as its behavior for the apparition as a whole. Utilizing measurements obtained on a total of 13 nights between February 9, 1996, and April 14, 1996, we find that the heliocentric distance (rH) dependence of the production rates of OH and NH were much shallower than those for either the carbon-bearing species or the visible dust. Based on the OH measurements, the derived water rH-dependence was also significantly less steep than expected from a basic water vaporization model and required an effective active surface area of about 29 km2 at rH=1.8 AU, 16 km2 at rH=1 AU, and only 13 km2 at rH=0.6 AU. This decrease in active area may be due to seasonally induced variations of a heterogeneous surface, or due to a decreasing contribution of gas from icy grains in the innermost coma. The relative abundances of the minor gas species place Hyakutake into the ``typical'' category of comets in the A'Hearn et al. (1995, Icarus118, 223-270) taxonomic classification system. The spectrum is generally redder at shorter wavelengths throughout the apparition; however, the dust color progressively changes from being significantly reddened (37%/1000 Å) at large rH to near-solar at small rH. This change of color with distance implies a significant change in grain sizes or a changing proportion between two or more grain populations. A major outburst was initiated near March 19.9, just prior to the comet's close approach to Earth. The characteristic recovery from the outburst differed among the observed species, with OH recovering most rapidly, essentially returning to its baseline values by March 25. The spatial radial fall-off of OH throughout this interval was consistent with the expected nominal spatial distribution, while CN and C2 displayed fall-offs consistent with a distributed source, and the dust fall-off was significantly less steep than 1/ρ, possibly due to fragmenting grains. Rotational lightcurve amplitudes were largest for the OH, NH, and dust, again consistent with the carbon-bearing species primarily originating from a distributed source. Significant variations were observed in the lightcurve amplitude and phase shifts as functions of aperture size. Finally, a refined value for the rotation period of 0.2614+/-0.0003 day was determined.
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Title: |
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Solitary potentials in cometary dusty plasmas |
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Authors: |
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Journal: |
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Geophysical Research Letters, Volume 29, Issue 18, pp. 17-1, CiteID 1870, DOI 10.1029/2002GL015219 (GeoRL Homepage) |
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Publication Date: |
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09/2002 |
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Origin: |
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AGU |
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AGU Keywords: |
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Space Plasma Physics: Electrostatic structures, Space Plasma Physics: Nonlinear phenomena, Planetology: Solar System Objects: Comets, Space Plasma Physics: General or miscellaneous, |
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Abstract Copyright: |
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(c) 2002: American Geophysical |
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Bibliographic Code: |
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2002GeoRL..29r..17M |
Recent observations reveal that plasmas in cometary tails contain charged dust grains of positive and negative polarities. Our objective here is to show that such a two-component dusty plasma supports dust-Langmuir and dust-acoustic waves. The latter in the nonlinear regime propagate in the form of localized negative potentials. The role of large amplitude potential structures for trapping the positive dust grains and for the formation of dust layers of opposite polarity is discussed.
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Title: |
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A Search for N+2 in Spectra of Comet C/2002 C1 (Ikeya-Zhang) |
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Authors: |
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Affiliation: |
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AA(Department of Astronomy, University of Texas at Austin, RLM 15.308, C-1400, Austin, TX 78712-1083 anita@barolo.as.utexas.edu) |
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Journal: |
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The Astrophysical Journal, Volume 576, Issue 2, pp. L165-L168. (ApJ Homepage) |
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Publication Date: |
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09/2002 |
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Origin: |
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UCP |
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ApJ Keywords: |
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Comets: Individual: Ikeya-Zhang (C/2002 C1), Solar System: Formation |
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Abstract Copyright: |
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(c) 2002: The American Astronomical Society |
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DOI: |
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Bibliographic Code: |
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2002ApJ...576L.165C |
We report low- and high-resolution
spectra of comet C/2002 C1 (Ikeya-Zhang) from the McDonald Observatory. The
comet has a well-developed ion tail including CO+, CO+2,
CH+, and H2O+. We used our high-resolution
spectra to search for N+2. None was detected, and we
placed upper limits on N+2/CO+ of 5.4×10-4.
N+2 was detected in the low-resolution spectra, but we
show that this emission was probably telluric in origin (if cometary, we derive
N+2/CO+=5.5×10-3, still very low).
We discuss the implications for the conditions in the early solar nebula of the
nondetection of N+2. These depend on whether the H2O
ice was deposited in the amorphous or crystalline form. If H2O was
deposited in its crystalline form, the detection of
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Title: |
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A Search for Argon and O VI in Three Comets Using the Far Ultraviolet Spectroscopic Explorer |
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Authors: |
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Weaver, H. A.; Feldman, P. D.; Combi, M. R.; Krasnopolsky, V.; Lisse, C. M.; Shemansky, D. E. |
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Affiliation: |
|
AA(Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218; weaver@pha.jhu.edu, pdf@pha.jhu.edu.; Current address: Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723-6099 .), AB(Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218; weaver@pha.jhu.edu, pdf@pha.jhu.edu.), AC(Department of Atmospheric, Oceanic, and Space Sciences, 1417A Space Research Building, University of Michigan at Ann Arbor, 2455 Hayward Street, Ann Arbor, MI 48109-2143 mcombi@engin.umich.edu.), AD(Department of Physics, Catholic University of America, 620 Michigan Avenue, NE, Washington, DC 20064; vkrasn@verizonmail.com.), AE(Department of Astronomy, University of Maryland, College Park, MD 20742; lisse@astro.umd.edu.), AF(Department of Aerospace Engineering, University of Southern California, 854 West 36th Place, Los Angeles, CA 90089-1191 dons@hippolyta.usc.edu.) |
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Journal: |
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The Astrophysical Journal, Volume 576, Issue 1, pp. L95-L98. (ApJ Homepage) |
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Publication Date: |
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09/2002 |
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Origin: |
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UCP |
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ApJ Keywords: |
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Comets: General, Comets: Individual: Alphanumeric: C/1999 T1, Comets: Individual: Alphanumeric: C/2000 WM1, Comets: Individual: Alphanumeric: C/2001 A2, Ultraviolet: Solar System |
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Abstract Copyright: |
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(c) 2002: The American Astronomical Society |
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DOI: |
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Bibliographic Code: |
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2002ApJ...576L..95W |
We conducted a sensitive search for the resonance lines of Ar I (λλ1048.22, 1066.66) and O VI (λλ1031.93, 1037.62) in the spectra of three long-period comets observed with the Far Ultraviolet Spectroscopic Explorer (FUSE). Argon emission was not detected from C/1999 T1 (McNaught-Hartley), C/2001 A2 (LINEAR), or C/2000 WM1 (LINEAR). Compared with the solar value, the [Ar/O] ratio is depleted in C/A2 by at least a factor of 10 and in C/WM1 by at least a factor of 13. The [Ar/O] upper limit for C/T1 is essentially the solar value, as our measurement was much less sensitive for that case. We also detected CO, which has a volatility similar to that of argon, during the FUSE observations. C/T1 was CO-rich ([CO/H2O] ~ 13%), while both C/A2 and C/WM1 were CO-poor ([CO/H2O] ~ 0.7% for C/A2 and ~0.4% for C/WM1). The argon and CO depletions in C/A2 and C/WM1 suggest formation temperatures >~60 K for both of these comets. The high CO abundance and upper limit on the argon abundance in C/T1 suggest that its formation temperature was in the range of ~40-50 K. No O VI emission was detected from comets C/T1 or C/A2, but the stronger line was marginally detected in C/WM1.
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Title: |
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Far Ultraviolet Spectroscopic Explorer Observations of CO and H2 Emission in Comet C/2001 A2 (LINEAR) |
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Authors: |
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Affiliation: |
|
AA(Department of Physics and Astronomy, Johns Hopkins University, Charles and 34th Street, Baltimore, MD 21218; pdf@pha.jhu.edu), AB(Department of Physics and Astronomy, Johns Hopkins University, Charles and 34th Street, Baltimore, MD 21218; pdf@pha.jhu.edu; Current address: Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723-6099.), AC(Department of Physics and Astronomy, Johns Hopkins University, Charles and 34th Street, Baltimore, MD 21218; pdf@pha.jhu.edu) |
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Journal: |
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The Astrophysical Journal, Volume 576, Issue 1, pp. L91-L94. (ApJ Homepage) |
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Publication Date: |
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09/2002 |
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Origin: |
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UCP |
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ApJ Keywords: |
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Comets: Individual: Alphanumeric: C/2001 A2, Ultraviolet: Solar System |
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Abstract Copyright: |
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(c) 2002: The American Astronomical Society |
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DOI: |
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Bibliographic Code: |
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2002ApJ...576L..91F |
Observations of comet C/2001 A2 (LINEAR) were made with the Far Ultraviolet Spectroscopic Explorer beginning 2001 July 12.58 and coinciding with a photometric increase of ~1.5 mag. Spectra were obtained in the 905-1180 Å range at 0.25 Å spectral resolution using the 30''×30'' aperture. Several new cometary emissions were identified, particularly the (0,0) bands of the CO Hopfield-Birge systems C-X and B-X at 1088 and 1151 Å, respectively, O I (1D-1D) at 1152 Å, and three lines of the H2 Lyman system at 1071.6, 1118.6, and 1166.8 Å, pumped by solar Lyβ fluorescence. Also detected were O I multiplets at 989, 1027, and 1040 Å and several lines of the H I Lyman series. The rotational envelopes of the CO bands are resolved and appear to consist of both ``cold'' and ``hot'' components, the cold component accounting for 70% of the flux and with a rotational temperature of 55+/-5 K. The hot component may be indicative of a CO2 source. The CO bands, H2 lines, and O I λ1152 all decreased by a factor of 2 over the 7.5 hr observation. The derived time-averaged production rates are Q(CO)=1.3×1027 molecules s-1 and Q(H2O)=2.1×1029 molecules s-1. These values may be uncertain by as much as a factor of 2 because of uncertainties in the solar flux and the electron impact contribution to the excitation.
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Title: |
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Runaway Fragmentation of Sungrazing Comets Observed with the Solar and Heliospheric Observatory |
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Authors: |
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Affiliation: |
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AA(Jet Propulsion Laboratory, California Institute of
Technology, |
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Journal: |
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The Astrophysical Journal, Volume 576, Issue 2, pp. 1085-1089. (ApJ Homepage) |
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Publication Date: |
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09/2002 |
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Origin: |
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UCP |
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ApJ Keywords: |
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Comets: General, Methods: Data Analysis |
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Abstract Copyright: |
|
(c) 2002: The American Astronomical Society |
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DOI: |
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Bibliographic Code: |
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2002ApJ...576.1085S |
The observed clustering of the
Solar and Heliospheric Observatory (SOHO) sungrazing comets is a product of
runaway fragmentation that occurs throughout their orbits about the Sun. Since
the sungrazers in tight pairs occasionally appear simultaneously in the field
of view of the
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Title: |
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An advanced physical model of cometary activity |
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Authors: |
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Rodionov, A. V.; Crifo, J.-F.; Szegő, K.; Lagerros, J.; Fulle, M. |
|
Affiliation: |
|
AA(Central Research Institute on Machine Building (TsNIIMASH), Pionyerskaya St., 4, Korolev, 141070, Moscow Region, Russia), AB(Service d'Aéronomie du CNRS, BP 3, F 91371 Cedex, Verrières le Buisson, France), AC(KFKI Research Institute for Particles and Nuclear Physics, PO Box 49, H 1525, Budapest, Hungary), AD(Uppsala Observatory, Box 515, S 75120, Uppsala, Sweden), AE(Osservatorio Astronomico di Trieste, Via Tiepolo, 11, I-34131, Trieste, Italy) |
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Journal: |
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Planetary and Space Science, Volume 50, Issue 10-11, p. 983-1024. (P&SS Homepage) |
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Publication Date: |
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08/2002 |
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Origin: |
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ELSEVIER |
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Bibliographic Code: |
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2002P&SS...50..983R |
We describe the present state of an advanced physical model aimed at the simulation of the environment of active cometary nuclei. The model can handle the complicated shapes of real cometary nuclei, and is ready to handle alternative assumptions concerning the nucleus composition and structure; its present version is based on the simple, but hitherto highly successful, Whipple (1950) paradigm: at small heliocentric distances, strong sublimation theory is used to compute the surface gas production, taking into account the time-dependent heat flow in the nucleus interior; at large distances, different types of gas molecules may be assumed to dominate the gas production. Any size and shape distribution of dust can be assumed. The nucleus spin motion is modelled with allowance for the outgassing and solar tidal torques. The gas outflow is computed by solving quasistationary flow equations (Euler, or Navier-Stokes), hence the extent of the coma which can be modelled is limited either by the breakdown of the fluid approximation, or by that of the steady-state approximation. The dust outflow is computed by solving quasi-stationary ``zero-temperature'' multifluid Eulerian equations in the gas-dust interaction region, and from a ``Keplerian fountain model'' beyond it: the extent of the dust distribution which can be modelled is only limited by computer resources limitations. In addition to the detailed gas and dust coma structure, the resulting net nucleus mass loss, net sublimation recoil force, net sublimation torque, and net thermal emission are computed. We mention the past applications of the model to comets P/Halley and C/Hyakutake, and indicate some of the future steps of development of the model.
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Title: |
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Theoretical aspects and interpretation of thermal measurements concerning the subsurface investigation of a cometary nucleus |
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Authors: |
|
|
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Affiliation: |
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AA(Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Wilhelmstr. 10, D-48149, Münster, Germany), AB(Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Wilhelmstr. 10, D-48149, Münster, Germany) |
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Journal: |
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Planetary and Space Science, Volume 50, Issue 9, p. 929-937. (P&SS Homepage) |
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Publication Date: |
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08/2002 |
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Origin: |
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ELSEVIER |
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Bibliographic Code: |
|
2002P&SS...50..929K |
Part of the lander payload for the comet rendezvous mission Rosetta is the thermal probe multi-purpose sensors for surface and subsurface science (MUPUS). In this paper, we discuss the relationship of the expected MUPUS data to structural and textural parameters of the near-surface layers of the cometary nucleus. Such properties could be crucial parameters concerning the formation and evolution of the nucleus. Thus, we calculate the thermal conductivity of a porous material in terms of microstructural parameters, using a geometrical model with a solid matrix, a surrounding pore space and a distinct contact area between different particles. We include the possibility that a significant amount of heat may be transported by pore filling vapour in addition to heat conducted via the matrix. Furthermore, we consider that the heat is transmitted through only a fraction of the grains and these are organized into a chain-like structure. These chains-and not the single grains-should be regarded as the basic unit of structure. Applying our model to measured thermal conductivities of porous water ice, we interpret the material in terms of microparameters and estimate the effective size of the contact area and the effective pore radius. The results are in good agreement with our knowledge of the prepared samples. Contrary, we can also show that popular models used in cometary research do not fit with laboratory data at all.
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Title: |
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Polarimetric study of levitating dust aggregates with the PROGRA2 experiment |
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Authors: |
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Hadamcik, E.; Renard, J. B.; Levasseur-Regourd, A. C.; Worms, J. C. |
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Affiliation: |
|
AA(CNRS Aéronomie, BP3, 91371, Verriéres-le-Buisson, France), AB(LPCE-CNRS, 3A avenue de la Recherche Scientifique, 45071, Cedex 2, Orléans, France), AC(CNRS Aéronomie, BP3, 91371, Verriéres-le-Buisson, France), AD(ESSC-ESF, c/o ENSPS-Parc d'Innovation, Boulevard S. Brandt, 67400, Illkirch France) |
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Journal: |
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Planetary and Space Science, Volume 50, Issue 9, p. 895-901. (P&SS Homepage) |
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Publication Date: |
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08/2002 |
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Origin: |
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ELSEVIER |
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Bibliographic Code: |
|
2002P&SS...50..895H |
In order to interpret polarimetric remote observations of solar system dust clouds (e.g. cometary coma dust), laboratory measurements are needed. Three samples composed of aggregates are studied: crystallized enstatite, pyrogenic alumina and titanium oxide. The new version of the PROGRA2 instrument allows to obtain polarimetric images of the samples under levitation. The dependence of polarization with phase angle and particle size is studied, as well as the effect of the porosity of the particles. Values of polarization at small phase angles are also discussed. The polarization near /90° decreases when the agglomerate size increases and when the porosity increases.
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Title: |
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Dielectric properties of comet analog refractory materials |
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Authors: |
|
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Affiliation: |
|
AA(Laboratoire de Planétologie de Grenoble, UJF/CNRS, Grenoble, France), AB(Centre de Recherche sur les Trés Basses Temperature, CNRS,, Grenoble, France), AC(Laboratoire de Planétologie de Grenoble, UJF/CNRS, Grenoble, France), AD(Laboratoire de Planétologie de Grenoble, UJF/CNRS, Grenoble, France) |
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Journal: |
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Planetary and Space Science, Volume 50, Issue 9, p. 857-863. (P&SS Homepage) |
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Publication Date: |
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08/2002 |
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Origin: |
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ELSEVIER |
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Bibliographic Code: |
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2002P&SS...50..857H |
Ground penetrating radio waves or
radar provide a promising technique for the study of sub-surface planetary or
cometary material. The comet nucleus sounding experiment by radiowave
transmission (CONSERT) will be the only experiment on board the ROSETTA mission
to provide information on the interior of the comet Wirtanen. Other projects planned
or under development are Marsis/Mars Express and GPR for Net Lander. The aim is
to perform a radar tomography, and the necessary data inversion of the measured
permittivity requires knowledge of the complex dielectric permittivities of
probable sub-surface materials, so laboratory studies of the dielectric
properties of analog geological materials have become necessary. In connection
with the Rosetta mission, we have characterized the dielectric permittivity of
dunite, montmorillonite and kaolinite. We used granular materials identical to
those of the KOSI comet simulation experiment conducted at DLR in
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Title: |
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Modelling the astronomical silicate features - I. On the spectrum subtraction method |
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Authors: |
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Affiliation: |
|
AA(National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China; Princeton University Observatory, Peyton Hall, Princeton, NJ 08544, USA; Theoretical Astrophysics Program, University of Arizona, Tucson, AZ 85719, USA), AB(Raymond and Beverly Sackler Laboratory for Astrophysics, University of Leiden, Postbus 9504, 2300 RA Leiden, the Netherlands), AC(National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China) |
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Journal: |
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Monthly Notices of the Royal Astronomical Society, Volume 334, Issue 4, pp. 840-846. (MNRAS Homepage) |
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Publication Date: |
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08/2002 |
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Origin: |
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MNRAS |
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Abstract Copyright: |
|
(c) RAS |
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DOI: |
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Bibliographic Code: |
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2002MNRAS.334..840L |
The assumption of additive absorptivity by different components in compound particles is a widely used method applied in the literature to the analysis of the chemical and structural properties of astronomical (circumstellar, interstellar, protostellar and cometary) silicates as well as other materials. The errors intrinsic in this additivity assumption, which, in application to astronomical spectra, amounts in some cases to spectrum subtraction, have not always been adequately considered in previous works on silicate mineralogy. The failings in the `spectrum subtraction method' (intrinsically the same as the additive absorptivity assumption) are discussed here in terms of silicate core-ice mantle grains with various shapes. It is shown that these assumptions result in substantial errors for spherical grains. For spheroidal grains, the errors are less significant and the spectrum subtraction method can be used to remove the ice mantle effects. It is demonstrated that there is no significant improvement by considering a distribution of spheroidal shapes. It is further shown that the presence of additional organic mantles substantially modifies the silicate mineralogy interpretation.
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Title: |
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On the source of C(1D) atoms in cometary comae |
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Authors: |
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Affiliation: |
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AA(Department of Mathematics & Astronomy, |
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Journal: |
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Monthly Notices of the Royal Astronomical Society, Volume 334, Issue 3, pp. 563-568. (MNRAS Homepage) |
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Publication Date: |
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08/2002 |
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Origin: |
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MNRAS |
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MNRAS Keywords: |
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molecular process; comets: individual: Comet Halley; comets: individual: Comet West; comets: individual: Comet Bradfield (1979 X) |
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Abstract Copyright: |
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(c) 2002 Blackwell Science Ltd |
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DOI: |
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Bibliographic Code: |
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2002MNRAS.334..563S |
The two mechanisms known for the production of cometary C(1D) atoms, namely the dissociative electron recombination of CO+ ions and the photodissociation of CO molecules, have been examined to ascertain whether these mechanisms can produce the observed brightnesses of the comae of Comet 1P/Halley, Comet C/1975 V1 (Comet West 1976 VI) and Comet C/1979 Y1 (Comet Bradfield 1979 X) in the CI (1D-1Po) line at 1931Å on specific dates. The brightnesses computed from these mechanisms for the respective comets are compared with those quoted in the literature. It is found that the latter of the above two mechanisms can account for the observed brightnesses of these comets in the CI (1D-1Poh) line. A valid, hitherto undiscussed reaction mechanism not involving COH for the production of cometary C(1D) atoms is suggested.
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Title: |
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Unidentified Bands in Comet Ikeya-Zhang (C/2002 C1): The Correlation between Unidentified Bands and H2O+ |
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Authors: |
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|
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Affiliation: |
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AA(Gunma Astronomical Observatory, 6860-86 Nakayama,
Takayama, Gunma 377-0702, |
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Journal: |
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The Astrophysical Journal, Volume 574, Issue 2, pp. L183-L185. (ApJ Homepage) |
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Publication Date: |
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08/2002 |
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Origin: |
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UCP |
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ApJ Keywords: |
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Comets: General, Comets: Individual: Ikeya-Zhang (C/2002 C1), Molecular Data |
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Abstract Copyright: |
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(c) 2002: The American Astronomical Society |
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DOI: |
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Bibliographic Code: |
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2002ApJ...574L.183K |
We report the results of the low-dispersion spectroscopic observations of comet Ikeya-Zhang (C/2002 C1) performed from 2002 March 10 to 20. The unidentified molecular bands that have been recognized in the plasma tail of several comets are detected in an antisunward coma of the comet Ikeya-Zhang. Our observations show the flux of unidentified bands at 5310 Å is correlated to the flux of H2O+ as reported for three comets by S. Wyckoff et al. The observed column density ratio between H2O+ and CO+, and the flux ratio between the unidentified bands and CO+ varied day by day, by a factor of ~2 in our observations. However, it appears that the ratios are proportional to each other. We conclude that a parent of unidentified bands is produced from or generates H2O+ directly or indirectly. We propose the hypothesis that H2O+ is the parent of the unidentified bands since similar structures of emission bands are recognized in some laboratory studies on charge transfer collisions between neutral water and Ar+ or N+2.
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Title: |
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Radio continuum observations of Comet C/1999 S4 (LINEAR) before, during, and after break-up of its nucleus |
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Authors: |
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Altenhoff, W. J.; Bertoldi, F.; Menten, K. M.; Sievers, A.; Thum, C.; Kreysa, E. |
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Affiliation: |
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AA(Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany wja@mpifr-bonn.mpg.de), AB(Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany fbertoldi@mpifr-bonn.mpg.de), AC(Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany ekreysa@mpifr-bonn.mpg.de), AD(Institute for Radio Astronomy at Millimeter Wavelengths (IRAM) Avenida Divina Pastora 7, 18012 Granada, Spain sievers@iram.es), AE(Institute for Radio Astronomy at Millimeter Wavelengths (IRAM) Domaine Universitaire de Grenoble, 300 rue de la piscine, 38406 St. Martin d'Hères, France thum@iram.fr), AF(Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany kmenten@mpifr-bonn.mpg.de) |
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Journal: |
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Astronomy and Astrophysics, v.391, p.353-360 (2002) (A&A Homepage) |
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Publication Date: |
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08/2002 |
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Origin: |
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A&A |
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A&A Keywords: |
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comets: general, comets: individual: C/1999 S4, radio continuum: solar system |
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DOI: |
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Bibliographic Code: |
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2002A&A...391..353A |
We observed radio continuum emission from Comet C/1999 S4 before, during, and after break-up of its nucleus. The detections before break-up indicate a photometric diameter of 4.7 km, from which we estimate that the nuclear diameter was about 0.9 km. We derive a dust production rate of ~ 9*E4 g s-1, corresponding to 0.03 g s-1 per square meter of the nuclear surface area, which is comparable to the values found for comets 1P/Halley and C/1995 O1 (Hale-Bopp). The implied gas-to-dust mass production ratio was between 2 and 5. The high daily erosion rate and the continuous fragmentation over months, as derived from water production rates, could not be confirmed. The low radio emission of the fragments directly after the break-up and their low cometary activity may be explained by their low surface temperatures. The published optical and most radio data support that the main nuclear decay started July 23, 2000. Our upper limits on the flux density obtained after the nuclear disintegration put an upper bound on the particulate dust mass released during that event. A scenario in which most of the nucleus disintegrated into many big boulders and part of it into a dust cloud is consistent with our observations.
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Title: |
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On the Return of Comet Grigg-Skjellerup |
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Authors: |
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|
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Affiliation: |
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AA(Kazan State University, Kremlevskaya ul. 18, Kazan, 420008 Tatarstan, Russia), AB(Chelyabinsk Agro-Technical University, Chelyabinsk, Russia), AC(Southern Urals State University, pr. Lenina 76, Chelyabinsk, 454080 Russia) |
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Journal: |
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Solar System Research, v. 36, Issue 4, p. 348-352 (2002). |
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Publication Date: |
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07/2002 |
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Origin: |
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KLUWER |
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Abstract Copyright: |
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(c) 2002 Kluwer Academic Publishers |
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Bibliographic Code: |
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2002SoSyR..36..348K |
Comet Grigg-Skjellerup must return to its perihelion on November 29, 2002. Before that, it will pass by Jupiter at a distance of 0.5 AU. A simulation of the meteor swarm that is related to this comet in origin has been made for 19 perihelia since 1907. Particles ejected from the nucleus at velocities +/-40 m/s in the direction perpendicular to its radius vector are concentrated around the comet and do not approach the Earth, while for particles ejected at velocities +/-60 m/s, conditions for the encounter with Jupiter are different; they approach Jupiter to a distance of 0.1 AU, then pass near the Earth's orbit at a distance of 0.01 AU. However, these particles have substantially different radiant coordinates and hardly form a flow of sufficient density.
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Title: |
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Multi-transitional observations of methanol in Comet Hale-Bopp (1995 O1) |
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Authors: |
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Ikeda, M.; Kawaguchi, K.; Takakuwa, S.; Sakamoto, A.; Sunada, K.; Fuse, T. |
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Affiliation: |
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AA(Nobeyama Radio Observatory, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan), AB(Nobeyama Radio Observatory, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan), AC(Nobeyama Radio Observatory, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan), AD(Nobeyama Radio Observatory, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan), AE(Nobeyama Radio Observatory, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan), AF(Subaru Telescope, National Astronomical Observatory of Japan 650 North A'ohoku Place, Hilo, Hawaii 96720, USA) |
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Journal: |
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Astronomy and Astrophysics, v.390, p.363-367 (2002) (A&A Homepage) |
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Publication Date: |
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07/2002 |
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Origin: |
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A&A |
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A&A Keywords: |
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comets: general, comets: individual: C/1995 O1(Hale-Bopp), ISM: abundances |
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DOI: |
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|
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Bibliographic Code: |
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2002A&A...390..363I |
We have observed 9 rotational
lines of methanol in comet Hale-Bopp (1995 O1) using the 45-m radio telescope
at Nobeyama Radio Observatory in the frequency range 36-104 GHz. The observed
transitions have upper state rotational energy levels of Eu = 7-159
K. Assuming the Haser model for density distribution, we estimated the
excitation temperature and the production rate to be
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Title: |
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Radial mixing in protoplanetary accretion disks. III. Carbon dust oxidation and abundance of hydrocarbons in comets |
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Authors: |
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|
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Affiliation: |
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AA(Institut für Theoretische Astrophysik, Universität
Heidelberg, Tiergartenstraße 15, 69121 |
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Journal: |
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Astronomy and Astrophysics, v.390, p.253-265 (2002) (A&A Homepage) |
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Publication Date: |
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07/2002 |
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Origin: |
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A&A |
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A&A Keywords: |
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accretion, accreation disks, molecular processes, solar system: formation, comets: general |
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DOI: |
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|
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Bibliographic Code: |
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2002A&A...390..253G |
The oxidation of carbon dust and its conversion into CO and some hydrocarbon compounds as intermediate products is studied for protoplanetary accretion discs. The disc model is based on the one-zone alpha -disc approximation. The radial mixing of the combustion products into the cold outer disc region by turbulent diffusion is considered in the transport-diffusion-reaction equations for the chemistry. It is shown that considerable amounts of CH_4 and C_2H_2 formed as by-products of carbon oxidation are mixed into cold disc regions beyond a distance of 10 AU where they can be included into the ice mixture of cometary nuclei formed in that region. This may explain the high abundance of these gases recently observed in comets Hyakutake (C/1996 B2) and Hale-Bopp (C/1995 O1). This mixing of hydrocarbons from carbon oxidation cannot, however, explain the high abundance of some other molecular species like C2H6 or CH3OH, which have to be formed by different processes.
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Title: |
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Large-scale disturbance of the solar wind by a comet |
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Authors: |
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|
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Affiliation: |
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AA(Max-Planck-Institut für Astrophysik, 85748 |
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Journal: |
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Astronomy and Astrophysics, v.389, p.1039-1046 (2002) (A&A Homepage) |
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Publication Date: |
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07/2002 |
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Origin: |
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A&A |
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A&A Keywords: |
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comets: general, Sun: solar wind |
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DOI: |
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|
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Bibliographic Code: |
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2002A&A...389.1039W |
Model calculations for the interaction of the solar wind with a comet are presented that extend 30 million km into the tail. It is shown that the disturbance of the interplanetary magnetic field (IMF) (the draping) is limited to timescales of 10 to 50 hours and length scales of 10 to 50 million km. This is supported by a theoretical argument about the acceleration of the cometary ions. The distribution of ions and protons at the end of the model tails agrees with measurements made by Ulysses far in the tail of comet Hyakutake. It is shown that the ion tail is concentrated in the current sheet between two flux lobes as long as the draping persists. The far tail, however, is flat and concentrated in a plane parallel to the IMF.
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Title: |
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Solar system objects in the ISOPHOT 170 mu m serendipity survey |
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Authors: |
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|
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Affiliation: |
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AA(Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany; ISO Data Centre, Astrophysics Division, Space Science Department of ESA, Villafranca, PO Box 50727, 28080 Madrid, Spain (until Dec. 2001)), AB(ISOPHOT Data Centre, Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany), AC(ISOPHOT Data Centre, Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany) |
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Journal: |
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Astronomy and Astrophysics, v.389, p.665-679 (2002) (A&A Homepage) |
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Publication Date: |
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07/2002 |
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Origin: |
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A&A |
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A&A Keywords: |
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minor planets, asteroids, comets: general, planets and satellites: general, infrared: solar system, surveys |
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DOI: |
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Bibliographic Code: |
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2002A&A...389..665M |
The ISOPHOT Serendipity Survey
(ISOSS) covered approximately 15% of the sky at a wavelength of 170 mu m while
the ISO satellite was slewing from one target to the next. By chance, ISOSS slews
went over many solar system objects (SSOs). We identified the comets, asteroids
and planets in the slews through a fast and effective search procedure based on
N-body ephemeris and flux estimates. The detections were analysed from a
calibration and scientific point of view. Through the measurements of the
well-known asteroids Ceres, Pallas, Juno and Vesta and the planets Uranus and
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Title: |
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Colors of Minor Bodies in the Outer Solar System. A statistical analysis |
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Authors: |
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|
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Affiliation: |
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AA(European Southern Observatory, Casilla 19001, Santiago, Chile), AB(European Southern Observatory, Casilla 19001, Santiago, Chile; Observatoire de Paris-Meudon, 5 place Jules Janssen, 92195 Meudon Cedex, France) |
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Journal: |
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Astronomy and Astrophysics, v.389, p.641-664 (2002) (A&A Homepage) |
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Publication Date: |
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07/2002 |
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Origin: |
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A&A |
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A&A Keywords: |
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comets: general, Kuiper Belt, solar system: general, methods: statistical |
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DOI: |
|
|
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Bibliographic Code: |
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2002A&A...389..641H |
We present a compilation of all available colors for 104 Minor Bodies in the Outer Solar System (MBOSSes); for each object, the original references are listed. The measurements were combined in a way that does not introduce rotational color artifacts. We then derive the slope, or reddening gradient, of the low resolution reflectance spectra obtained from the broad-band color for each object. A set of color-color diagrams, histograms and cumulative probability functions are presented as a reference for further studies, and are discussed. In the color-color diagrams, most of the objects are located very close to the ``reddening line'' (corresponding to linear reflectivity spectra). A small but systematic deviation is observed toward the I band indicating a flattening of the reflectivity at longer wavelengths, as expected from laboratory spectra. A deviation from linear spectra is noticed toward the B for the bluer objects; this is not matched by laboratory spectra of fresh ices, possibly suggesting that these objects could be covered with extremely evolved/irradiated ices. Five objects (1995 SM55, 1996 TL66, 1999 OY_3, 1996 TO66 and (2060) Chiron) have almost perfectly solar colors; as two of these are known or suspected to harbour cometary activity, the others should be searched for activity or fresh ice signatures. In the color-color diagrams, 1994 ES_2, 1994 EV_3, 1995 DA_2 and 1998 HK151 are located very far from the main group of objects; it is suspected that this corresponds to inaccurate measurements and not intrinsically strange objects. The color distributions were analyzed as functions of the orbital parameters of the objects and of their absolute magnitude. No significant correlation is observed, with the following exceptions: Cubewanos with low orbital excitation (low i, e and/or E = sqrt(e2 + sin 2 i)), and therefore experiencing on average fewer and less violent collisions have significantly redder colors; Cubewanos with faint absolute magnitude M(1,1) tend to be redder than the others, while Plutinos present the opposite trend. The color distribution of the various MBOSS classes are analyzed and compared using generic statistic tools. The comets were found to be significantly bluer than the other MBOSSes. Finally, we compare the various 1D and 2D color distributions to simple models, in order to throw some light on the question of the bimodality of MBOSS color distributions. It is found that with the current data set, all color distributions are compatible with simple, continuous distribution models, while some color distributions are not compatible with simple bimodal distribution models. Table 1 is also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/389/641, and the tables and complete set of figures corresponding the up-to-date database are available on the web at http://www.sc.eso.org/~ohainaut/MBOSS. Table 1 is also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/389/641 Tables 3, 5, 6 and the list of papers are only available in electronic form at http://www.edpsciences.org
|
Title: |
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The Deep Space 1 Encounter with Comet 19p/Borrelly |
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Authors: |
|
Boice, D. C.; Soderblom, L. A.; Britt, D. T.; Brown, R. H.; Sandel, B. R.; Yelle, R. V.; Buratti, B. J.; Hicks; Nelson; Rayman; Oberst, J.; Thomas, N. |
|
Affiliation: |
|
AA( Southwest Research Institute, Space Science and Engineering Division, P.O. Drawer 28510, San Antonio, Texas 78228-0510, USA dboice@swri.edu ), AB( United States Geological Survey, 2255 North Gemini Drive, Flagstaff, Arizona 86001, USA ), AC( University of Tennessee, Department of Geological Sciences, Knoxville, Tennessee 37996, USA ), AD( University of Arizona, Department of Planetary Sciences, Lunar and Planetary Laboratory, Tucson, Arizona 85721, USA ), AE( University of Arizona, Department of Planetary Sciences, Lunar and Planetary Laboratory, Tucson, Arizona 85721, USA ), AF( University of Arizona, Department of Planetary Sciences, Lunar and Planetary Laboratory, Tucson, Arizona 85721, USA ), AG( Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA ), AH( Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA ), AI( Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA ), AJ( Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA ), AK( DLR Institute of Space Sensor Technology and Planetary Exploration, Rutherfordstrasse 2, D-12489 Berlin, Germany ), AL( Max-Planck-Institut für Aeronomie, Max-Planck-Strasse 2, D-37191 Katlenburg-Lindau, Germany ) |
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Journal: |
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Earth, Moon, and Planets, v. 89, Issue 1, p. 301-324 (2002). (EM&P Homepage) |
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Publication Date: |
|
00/2002 |
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Origin: |
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KLUWER |
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Keywords: |
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Coma, comets, Deep Space 1, nucleus, spacecraft exploration |
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Bibliographic Code: |
|
2002EM&P...89..301B |
NASA's Deep Space 1 (DS1) spacecraft successfully encountered comet 19P/Borrelly near perihelion and the Miniature Integrated Camera and Spectrometer (MICAS) imaging system onboard DS1 returned the first high-resolution images of a Jupiter-family comet nucleus and surrounding environment. The images span solar phase angles from 88° to 52°, providing stereoscopic coverage of the dust coma and nucleus. Numerous surface features are revealed on the 8-km long nucleus in the highest resolution images (47-58 m pixel). A smooth, broad basin containing brighter regions and mesa-like structures is present in the central part of the nucleus that seems to be the source of jet-like dust features seen in the coma. High ridges seen along the jagged terminator lead to rugged terrain on both ends of the nucleus containing dark patches and smaller series of parallel grooves. No evidence of impact craters with diameters larger than about 200-m are present, indicating a young and active surface. The nucleus is very dark with albedo variations from 0.007 to 0.035. Short-wavelength, infrared spectra from 1.3 to 2.6 μm revealed a hot, dry surface consistent with less than about 10% actively sublimating. Two types of dust features are seen: broad fans and highly collimated ``jets'' in the sunward hemisphere that can be traced to the surface. The source region of the main jet feature, which resolved into at least three smaller ``jets'' near the surface, is consistent with an area around the rotation pole that is constantly illuminated by the sun during the encounter. Within a few nuclear radii, entrained dust is rapidly accelerated and fragmented and geometrical effects caused from extended source regions are present, as evidenced in radial intensity profiles centered on the jet features that show an increase in source strength with increasing cometocentric distance. Asymmetries in the dust from dayside to nightside are pronounced and may show evidence of lateral flow transporting dust to structures observed in the nightside coma. A summary of the initial results of the Deep Space 1 Mission is provided, highlighting the new knowledge that has been gained thus far.
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Title: |
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Comet Grains: Their IR Emission and Their Relation to ISm Grains |
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Authors: |
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|
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Affiliation: |
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AA( |
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Journal: |
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Earth, Moon, and Planets, v. 89, Issue 1, p. 247-287 (2002). (EM&P Homepage) |
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Publication Date: |
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00/2002 |
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Origin: |
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KLUWER |
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Keywords: |
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Amorphous carbon, CP IDPs, crystals, dust, Hale-Bopp, silicates |
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Bibliographic Code: |
|
2002EM&P...89..247W |
Comets and the chondritic porous
interplanetary dust particles (CP IDPs) that they shed in their comae are
reservoirs of primitive solar nebula materials. The high porosity and fragility
of cometary grains and CP IDPs, and anomalously high deuterium contents of
highly fragile, pyroxene-rich Cluster IDPs imply these aggregate particles
contain significant abundances of grains from the interstellar medium (ISM). IR
spectra of comets (3-40 μm) reveal the presence of a warm (near-IR) featureless
emission modeled by amorphous carbon grains. Broad and narrow resonances near
10 and 20 microns are modeled by warm chondritic (50% Fe and 50% Mg) amorphous
silicates and cooler Mg-rich crystalline silicate minerals, respectively.
Cometary amorphous silicates resonances are well matched by IR spectra of CP
IDPs dominated by GEMS (0.1 μm silicate spherules) that are thought to be the
interstellar Fe-bearing amorphous silicates produced in AGB stars. Acid-etched
ultramicrotomed CP IDP samples, however, show that both the carbon phase
(amorphous and aliphatic) and the Mg-rich amorphous silicate phase in GEMS are
not optically absorbing. Rather, it is Fe and
|
Title: |
|
Physico-Chemistry of Comets: Models and Laboratory Experiments |
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Authors: |
|
|
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Affiliation: |
|
AA( Leiden Observatory, P.O. Box 9513, 2300 RA Leiden, The Netherlands ), AB( Astrobiology Laboratory, Leiden Institute of Chemistry, P.O. Box 9502, 2300 RA Leiden, The Netherlands ), AC( Space Science Division, NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035, USA ) |
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Journal: |
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Earth, Moon, and Planets, v. 89, Issue 1, p. 221-246 (2002). (EM&P Homepage) |
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Publication Date: |
|
00/2002 |
|
Origin: |
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KLUWER |
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Keywords: |
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Comet C/1995 O1 Hale-Bopp, comets, laboratory studies, physico-chemsitry |
|
Bibliographic Code: |
|
2002EM&P...89..221E |
Until cometary matter can be studied in-situ or cometary samples are brought back to Earth for analysis, theoretical models and laboratory studies remain a crucial tool for revealing the nature of cometary matter. Constraints on the nature of the primordial material available for incorporation into comets and other solar system material comes from analysis of data from space-based and ground-based observatories. The structure of the nuclear ice component, which may have coexisting amorphous/crystalline phases and include clathrates and other trapped guest molecules, strongly influences the cometary outgassing properties. This paper reviews laboratory work on ice and carbonaceous compounds and discusses their significance for cometary chemistry. Special emphasis will be given to studies on the thermal processing of ices and their implications for the structure changes and subsequent release of volatiles. We also describe the preliminary results of a model of nuclear outgassing, and discuss how such models can be used to infer the chemical structure of the nuclear ices. Furthermore, we confront cometary data with the analysis of carbonaceous meteorites. Recent laboratory results on volatile compounds and the macromolecular structure of carbonaceous meteorites allow us to investigate the link of small bodies in the Solar System. Until ROSETTA will land on comet Wirtanen and study directly the nuclear composition, laboratory measurements of ice and refractory analogs will - together with the analysis of meteorites - significantly improve our knowledge on the origin and structure of comets.
|
Title: |
|
New Experimental and Theoretical Techniques for Studying Photochemical reactions of Cometary Atmospheres |
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Authors: |
|
Jackson, William M.; Xu, Dadong; Huang, Jianhua; Price, Roosevelt J.; Volman, David H. |
|
Affiliation: |
|
AA( Chemistry Department, University of California, Davis, One Shields Ave, Davis, CA 95616, USA wmjackson@ucdavis.edu), AB( Chemistry Department, University of California, Davis, One Shields Ave, Davis, CA 95616, USA), AC( Chemistry Department, University of California, Davis, One Shields Ave, Davis, CA 95616, USA), AD( Chemistry Department, University of California, Davis, One Shields Ave, Davis, CA 95616, USA), AE( Chemistry Department, University of California, Davis, One Shields Ave, Davis, CA 95616, USA) |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 197-220 (2002). (EM&P Homepage) |
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Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
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Keywords: |
|
Carbon disulfide, cometary atmosphere, ion imaging, photochemical reaction, sulfur branching ratio |
|
Bibliographic Code: |
|
2002EM&P...89..197J |
New experimental methods for studying photochemical reactions are given and the strength and weakness are briefly discussed. References and bibliographies for these photochemical studies are presented. A case study of carbon disulfide (CS2) that uses vacuum ultraviolet lasers, time-of-flight mass spectrometry, molecular beams and ion velocity imaging to measure and characterize the products is described. These results are compared with previous studies and the difficulties involved in understanding these results are pointed out.
|
Title: |
|
Composition of Comets: Observations and Models |
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Authors: |
|
|
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Affiliation: |
|
AA(Southwest Research Institute, P. O. Drawer 28510, |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 179-195 (2002). (EM&P Homepage) |
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Publication Date: |
|
00/2002 |
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Origin: |
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KLUWER |
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Keywords: |
|
Comets, composition |
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Bibliographic Code: |
|
2002EM&P...89..179H |
We analyze the chemical composition and abundances of comets based on in situ measurements of Comet 1P/Halley and remote sensing observations of several recent bright comets including Hale-BOPP (C/1995 O1) and Hyakutake (C/1996 B2), in light of the elemental abundances of the solar system. Nitrogen is underabundant in comets relative to the solar system because nitrogen tends to be in N2, which is chemically relatively inert. While many details remain uncertain, some gross features are emerging. The abundance of water : silicates: carbonaceous molecules (CO, CO2, and hydrocarbons) by mass is approximately 1 : 1 : 1. Furthermore, the mass abundance of ice : dust (silicates and hydrocarbon polycondensates) is about 1 : 1. We compare a list of identified comet molecules with molecules detected in the interstellar medium, although a comparison with their relative abundances, particularly in the ice phase, would be more meaningful. However, ice-phase abundances are not yet available. One can expect a variation of the abundances of carbon-bearing molecules in comets to be associated with their place of origin in the solar nebula. However, we also note that comets are heterogeneous. Thus, observed differences may be related to the place of origin, heterogeneity of the nucleus, or acquired through evolution. The molecular and elemental compositions of the coma are most likely not the same as those in the nucleus. This is particularly true for volatile ices and their gases and for the dust-to-ice and dust-to-gas ratios. Analyses must carefully consider the three sources of gas: Water from the surface of the nucleus, gases more volatile than water from the interior of the nucleus, and gases from the sublimation of the dust distributed in the coma. Topography on the surface of the nucleus may cause important evolutionary differences in the dust-to-gas mass ratio. Relatively inactive areas on the surface of the nucleus are probably associated with convex topography. Gas sublimated from convex areas (hills and mountains) diverges more strongly relative to gas sublimated from concave areas, which can entrain dust more efficiently. Thus, the entrainment of dust from convex areas is poor and dust may fall back to the surface of the nucleus creating a dust mantle, which further inhibits outgassing.
|
Title: |
|
Sublimation Mechanisms of Comet Nuclei |
|
Authors: |
|
|
|
Affiliation: |
|
AA(CNR, IASF,
Area di Ricerca di Tor Vergata, v. del Fosso del Cavaliere, 100 - 00133 Rome,
Italy) |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 161-178 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Comet, nucleus, sublimation |
|
Bibliographic Code: |
|
2002EM&P...89..161C |
In this paper the sublimation mechanisms of parent molecules from nuclei will be reviewed from the point of view of theoretical models, and the results of models will be compared with the results of the extensive observation campaign of C/1995 O1 Hale-Bopp. The simple model of a mixture of ices in which each gas sublimates independently from the others when the right temperature has been reached is in many cases inadequate to explain the observations. Many minor volatiles can be trapped in the amorphous water ice and released in a complex way when particular ranges of temperature are reached. The presence of sublimating icy grains in the inner coma of comets, suggested many years ago, seems now to be proven, at least for Hale-Bopp. From these grains a significant amount of water and other volatiles could contribute to the total flux measured in the coma. The unprecedented coverage of Hale-Bopp's gas production curve for such a long time and with so many instruments has offered to modellers a wonderful occasion to test and compare observation results with the predictions of sublimation models, demonstrating that current models are able to explain observed results.
|
Title: |
|
Rotational Properties of Cometary Nuclei |
|
Authors: |
|
|
|
Affiliation: |
|
AA( Laboratoire
d'Astrophysique de Marseille, BP 8, 13376 Marseille Cedex 12, France ), AB( Instituto de Astrofísica de Andalucía, c/ Camino Bajo de
Huétor, 24, Apartado 3004, 18080 Granada, Spain ) |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 135-160 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
C/1995 O1 (Hale-Bopp), 19P/Borrelly, 46P/Wirtanen, comets, modeling, nucleus, observations, rotation |
|
Bibliographic Code: |
|
2002EM&P...89..135J |
We review several techniques used to retrieve rotational parameters from observations. The spin period of a dozen of comets retrieved with these techniques are summarized. We describe how the spin period of comet Hale-Bopp (C/1995 O1) has been calculated with a high accuracy (11.30-11.34 h). Although several authors converged to a spin axis orientation at (α,δ) = (275 +/- 15°, -55 +/- 5°), detailed studies indicate that the dust jets morphology in 1996-1997 may be incompatible with this orientation. Comet 19P/Borrelly has been recently observed by the Deep Space 1 spacecraft. At the same time, its spin axis orientation and period have been determined by several authors to be respectively (α,δ) = (225 +/- 15°, -10 +/- 10°) and 26h. These two comets are likely to be in (or close to) a principal axis spin state. We discuss new modeling of the spin state of comet 46P/Wirtanen, the target of the Rosetta mission. The model involves a three-dimensional shape and thermal model, from which the torque of the nongravitational force is calculated at each time step. The moments of inertia are computed for each irregular shape. The results from numerical integrations show that this comet can remain in a principal axis spin state during more than 10 orbits if the spin period does not get above ~6 h. If the spin period increases, its nucleus gets rapidly into excited spin states. It shows that even small and very active short-period comets are not necessarily in nonprincipal axis spin states. In the last section, the consequences of recent observations and modeling of the rotational parameters of comet nuclei are discussed, and unsolved problems are presented.
|
Title: |
|
Observational Constraints On Surface Characteristics Of Comet Nuclei |
|
Authors: |
|
|
|
Affiliation: |
|
AA( Physics Department, University of Central Florida, Orlando, Florida 32816-2385, USA. campins@physics.ucf.edu ), AB( University of Hawaii, 2680 Woodlawn Drive, Honolulu, Hawaii 96822, USA ) |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 117-134 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Comets, nuclei, surfaces |
|
Bibliographic Code: |
|
2002EM&P...89..117C |
Direct observations of the nuclear surfaces of comets have been difficult; however a growing number of studies are overcoming observational challenges and yielding new information on cometary surfaces. In this review, we focus on recent determinations of the albedos, reflectances, and thermal inertias of comet nuclei. There is not much diversity in the geometric albedo of the comet nuclei observed so far (a range of 0.025 to 0.06). There is a greater diversity of albedos among the Centaurs, and the sample of properly observed TNOs (2) is still too small. Based on their albedos and Tisserand invariants, Fernández et al. (2001) estimate that about 5% of the near-Earth asteroids have a cometary origin, and place an upper limit of 10%. The agreement between this estimate and two other independent methods provide the strongest constraint to date on the fraction of objects that comets contribute to the population of near-Earth asteroids. There is a diversity of visible colors among comets, extinct comet candidates, Centaurs and TNOs. Comet nuclei are clearly not as red as the reddest Centaurs and TNOs. What Jewitt (2002) calls ultra-red matter seems to be absent from the surfaces of comet nuclei. Rotationally resolved observations of both colors and albedos are needed to disentangle the effects of rotational variability from other intrinsic qualities. New constraints on thermal inertia of comets are consistent with previous independent estimates. The thermal inertia estimates for Centaurs 2060 Chiron and 8405 Asbolus are significantly lower than predicted by thermal models, and also lower than the few upper limits or constraints known for active, ordinary nuclei.
|
Title: |
|
Comet Splitting - Observations and Model Scenarios |
|
Authors: |
|
|
|
Affiliation: |
|
AA(European Southern Observatory ESO, Alonso de Cordova 3107, Santiago de Chile) |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 91-115 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Appearance, boulders, classification, comet evolution, disappearing comets, double nuclei, dynamics, fragmentation models, Kreutz group comets, split comets, striae |
|
Bibliographic Code: |
|
2002EM&P...89...91B |
Splitting events affect cometary nuclei to a different level of severity ranging from complete disruption of the nucleus (e.g., C/1999 S4 LINEAR) to separation of major fragments (e.g., 73P/Schwassmann-Wachmann 3) and spill-offs of smaller boulders (e.g., C/2001 A2 LINEAR). Fragmentation of comets produces secondary products over a wide range of sizes (from cometesimals to sub-micron dust). It is detectable through the presence of fragments (with own comae and tails) in the coma of the parent nucleus, through outbursts in its activity and through arc-lets (``coma wings'') associated with fragments. The secondaries have different lifetimes and show different non-gravitational forces. Nucleus splitting is also considered to generate whole families of comets (Kreutz group) or - if gravitational bound - multiple nuclei (e.g., C/1995 O1 Hale-Bopp). It may explain the striae phenomena seen in dust tails of bright comets (C/1995 O1 Hale-Bopp) and the detection of chains of impact craters on other bodies in the solar system. As process of significant mass loss it is relevant for the scenario of nucleus extinction, at the same time it also plays a role for the number statistics of existing (observable) comets and for the size distribution of comet nuclei. Various model scenarios for nucleus splitting are proposed: tidal disruption, rotational splitting, break-up due to internal gas pressure, fragmentation due to collision with other bodies. Only in one case, Comet D/1993 F1 Shoemaker-Levy 9, the physical process of fragmentation could be undoubtedly identified. In any case, comet splitting provides important insights in the internal structure, surface layering and chemistry of comet nuclei.
|
Title: |
|
Hale-Bopp: What Makes a Big Comet Different? Coma Dynamics: Observations and Theory |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Department of Atmospheric, Oceanic and Space Sciences, |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 73-90 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Comet C/1995 O1 (Hale-Bopp), comets, dynamics, molecular processes |
|
Bibliographic Code: |
|
2002EM&P...89...73C |
Comet Hale-Bopp was the largest comet by almost any definition, observed at least since the advent of modern observing techniques. In a more typical comet both the chemical and dynamical influences of collisional processes are limited by the short time a parcel of gas sublimated from the nucleus remains in the dense part of the coma. The resulting large size of the collisional coma in comet Hale-Bopp had important consequences on the dynamics of the coma, which in turn has important consequences on how observations are interpreted with standard models. Measured velocities of typical gas species (mostly the observed radicals) as well as dust were larger than normal comets. Conversely, velocities of superthermal atomic hydrogen were smaller than normal because of the same collisional processes. Furthermore, as a consequence, dust particles, which are dragged by the outflowing gas, were also accelerated to larger velocities. Such larger velocities are not simply an interesting curiosity in their own right, because nearly all observations of dust and gas are interpreted with models of the coma that depend directly on some measurement or assumption with regard to velocity. In this presentation both observations and theory regarding the dynamical conditions in the coma of comet Hale-Bopp are summarized.
|
Title: |
|
Lessons of Comet Hale-Bopp for Coma Chemistry: Observations and Theory |
|
Authors: |
|
|
|
Affiliation: |
|
AA( Observatoire de Paris, F-92195 Meudon, France), AB( Observatoire de Paris, F-92195 Meudon, France ) |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 53-71 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Astrochemistry, Comet C/1995 O1 (Hale-Bopp), comets, molecular processes, molecules |
|
Bibliographic Code: |
|
2002EM&P...89...53B |
Many new cometary molecules - both parents and daughters - were detected in the exceptionally productive comet C/1995 O1 (Hale-Bopp). The space distribution of several of these species could be investigated from radio interferometry or from long-slit spectroscopy in the infrared. The distinction between parent species - directly sublimated from nucleus ices - and secondary species - resulting from chemical processing in the coma or produced by a secondary source - is not always clear. It is important to assess whether or not observed minor species (HCOOCH3, HCOOH ... ) could be synthesized by chemical reactions favoured by the high density of the coma of comet Hale-Bopp. Chemical modelling by Rodgers and Charnley suggests that this is not the case. CO and H2CO are abundant cometary species which partly come from distributed sources. The nature of these sources is still a mystery. A special case, now well documented, is that of HNC, for which the abundance evolution with heliocentric distance could be observed in comet Hale-Bopp and which was observed in several much less productive comets.
|
Title: |
|
Modeling the Comet Nucleus Interior |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Department of Geophysics and Planetary Sciences, |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 27-52 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Comet C/1995 O1 Hale-Bopp, comets, interiors, modelling |
|
Bibliographic Code: |
|
2002EM&P...89...27P |
Numerical simulation of the structure and evolution of a comet nucleus is reviewed both from the mathematical and from the physical point of view. Various mathematical procedures and approximations are discussed, and different attempts to model the physical characteristics of cometary material, such as thermal conductivity, or permeability to gas flow, are described. The evolution and activity of comets is shown to depend on different classes of parameters: Defining parameters, such as size and orbit, structural parameters, such as porosity and composition, and initial parameters, such as temperature and live radioisotope content. The latter are related to the formation of comets. Despite the large number of parameters, general conclusions, or common features, appear to emerge from the numerous model calculations - for different comets - performed to date. Thus, the stratified structure of comet nuclei, volatile depletion, and the role of crystallization of ice in cometary outbursts are discussed. Finally, an evolution model applied to comet C/1995 O1 Hale-Bopp - using different assumptions - is described and analysed in the light of observations.
|
Title: |
|
The Nucleus of Comet Hale-Bopp (C/1995 O1): Size and Activity |
|
Authors: |
|
|
|
Affiliation: |
|
AA(University of Hawaii, Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822, USA yan@ifa.hawaii.edu) |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 3-25 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Comets, Hale-Bopp |
|
Bibliographic Code: |
|
2002EM&P...89....3F |
A review of our current understanding of Comet Hale-Bopp's nuclear size is presented. Currently the best constraints on the effective radius are derived from late-1996 mid-IR data and near-perihelion radio data. Unfortunately the two regimes give differing answers for the radius. A possible reconciliation of the two datasets is presented that would place the radius at around 30 km. This is a large cometary radius compared to the others that are known, and this motivates a discussion of what makes a large comet different. From several possible large-comet properties, Hale-Bopp's activity is analyzed, focusing on the production rates, coma jet features, dust optical depth, and relationship with the interplanetary dust environment. The optical depth is particularly important since an optically-thick inner coma could complicate attempted measurements of the ``nucleus''.
|
Title: |
|
Cosmic Roulette: Comets In The |
|
Authors: |
|
|
|
Affiliation: |
|
AA( Campion College and Department of Physics, The University of Regina, Regina, SK, Canada ), AB( Department of Physics, The University of Regina, Regina, SK, Canada ) |
|
Journal: |
|
Earth, Moon, and Planets, v. 88, Issue 4, p. 211-221 (2000). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Asteroid impacts, Comet 28P/Neujmin 1, cometary nuclei, cometary outbursts |
|
Bibliographic Code: |
|
2002EM&P...88..211B |
We have produced top ten ranked lists of impact velocity, main belt asteroid region dwell times and impact probabilities for a selection of short period comets. The comet with the combined highest ranking with respect to impact probability and impact velocity is Comet C/1766 G1 Helfenzrieder. Since it is not clear that this comet still exists, the highest ranked, presently active, comet with respect to the likelihood of suffering impacts from meter-sized objects while in the main belt asteroid region is Comet 28P/Neujmin 1. We find no evidence to support the existence of a distinctive sub-set of the short period comets liable to show repeated outburst or splitting behaviours due to small body, meter-sized, asteroid impacts.
|
Title: |
|
Estimating The Dust Particle Size Of Comet Hale-Bopp By Studying The Motion Of The Ejecta On September 10-11, 1996 |
|
Authors: |
|
|
|
Affiliation: |
|
AA(National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China ), AB(National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China ), AC(National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China ) |
|
Journal: |
|
Earth, Moon, and Planets, v. 88, Issue 2, p. 61-74 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Comet Hale-Bopp, kinematics, outburst |
|
Bibliographic Code: |
|
2002EM&P...88...61Q |
We report the observation of an outburst of comet Hale-Bopp (C/1995 O1) happened on September 10-11, 1996, carried by the 1.56 m telescope of Shanghai Astronomical Observatory. Two ejecta were found in CCD images during the outburst. According to the positions of ejecta, we discuss the motion of the ejecta considering dust particles are subjected to the gravity and the Solar radiation pressure, and conclude that the mean radii of dust grains in the ejecta were about submicron-sized. So the observed X-ray emission are most likely produced by small size particles scattering the Solar X-ray.
|
Title: |
|
The shell of Comet Hale-Bopp |
|
Authors: |
|
|
|
Affiliation: |
|
AA( |
|
Journal: |
|
Chinese Astronomy and Astrophysics, Volume 26, Issue 3, p. 348-353. (ChA&A Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Keywords: |
|
Comet Hale, Bopp, shell, jet |
|
Bibliographic Code: |
|
2002ChA&A..26..348Y |
A film showing the shells in the coma of Comet Hale-Bopp, taken on March 4, 1997, is digitized and measured by means of a PDS. The method of fitting leads to the following results: (1)The first shell (innermost one), derived from a jet formation, is seen as an Archimedean spiral and the velocity of the ejecta from the cometary nucleus is 1.6 km/sec; (2)All of the 2nd, 3rd and 4th shells are parabolas or catenaries.
|
Title: |
|
Five main tail streamers of Comet Halley |
|
Authors: |
|
Zhao, Hai-Bin; Hu, Zhong-Wei; Wang, Jian-Zhong; Hou, Zhen-Yu |
|
Affiliation: |
|
AA(Department of Astronomy, Nanjing University, Nanjing 210093, China), AB(Department of Astronomy, Nanjing University, Nanjing 210093, China), AC(Department of Astronomy, Nanjing University, Nanjing 210093, China), AD(Department of Astronomy, Nanjing University, Nanjing 210093, China) |
|
Journal: |
|
Chinese Astronomy and Astrophysics, Volume 26, Issue 3, p. 339-347. (ChA&A Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Keywords: |
|
comet Halley, main tail streamer, aberration angle, photometry |
|
Bibliographic Code: |
|
2002ChA&A..26..339Z |
It is of much interest that Comet Halley displayed long and straight main tails (tail streamers) even at large heliocentric distances. Streamers are usually thought to be plasma in nature. However, a dust streamer may be seen superimposed on the main tail when the Earth is close to the comet's orbital plane. Because of the broad sensitive wave range of the photographic plate and of projection effect, both plasma and dust streamers may be superimposed in the image. In this paper, photometric and geometric measurements of five main tail streamers of Comet 1P/Halley at different heliocentric distances are made and compared. The brightness profiles along streamer axes, the full widths at half maximum (FWHMs) of several transverse cuts, the apparent and actual aberration (or lag) angles of the axes as well as the tail lengths are obtained. Among the streamers recorded on blue plates, two before the perihelion passage are definitely plasma streamers. The similarity of the photometry and geometric features of the five streamers and other lines of evidence suggest that the other three streamers are also mainly plasma streamers, while any contamination by dust would be secondary.
|
Title: |
|
Evolution of Comets into Asteroids |
|
Authors: |
|
|
|
Journal: |
|
Asteroids III, W. F. Bottke Jr., A. Cellino, P. Paolicchi, and R. P. Binzel (eds), University of Arizona Press, Tucson, p.669-686 |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
LPI |
|
Bibliographic Code: |
|
2002aste.conf..669W |
In the past decade, new observations and new research tools have afforded us a better understanding of the interrelationships between comets and asteroids. The extensive automated surveys for near-Earth objects (NEOs) have serendipitously discovered many objects in comet-like orbits. Dynamical simulation codes have improved to the point where we can simulate the detailed orbital behavior of large swarms of test particles as they move out from various storage reservoirs, such as the Oort cloud and the Kuiper belt. Physical studies of both comets and asteroids have given us a far better understanding of the nature of these bodies and have identified possible discriminators to be used in comparing them. As a result, we can now identify likely dormant or extinct comet candidates among the asteroid population. It appears that ~6 ± 4% (or perhaps more) of the NEO population is derived from Jupiter-family comets. Also, it is highly likely that many asteroids in eccentric orbits with large semimajor axes and large inclinations are derived from the Oort cloud. However, we must also recognize that some small fraction of the Oort cloud population is likely to consist of asteroidal bodies ejected there during the clearing of the planetary zones in the early solar system. Additional physical and dynamical studies are required to continue improving our knowledge of the interrelationships between comets and asteroids and to help identify likely extinct comet candidates.
|
Title: |
|
Photodegradation of hexamethylenetetramine by VUV and its relevance for CN and HCN extended sources in comets |
|
Authors: |
|
Cottin, Hervé; Bachir, Souleyman; Raulin, François; Gazeau, Marie-Claire |
|
Affiliation: |
|
AA(Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), UMR 7583 CNRS, Université Paris 7 and Paris 12, C.M.C., 61 Avenue du Général de Gaulle, 94010 Créteil Cedex, France) |
|
Journal: |
|
Advances in Space Research, Volume 30, Issue 6, p. 1481-1488. (AdSpR Homepage) |
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Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science B.V. All rights reserved. |
|
Bibliographic Code: |
|
2002AdSpR..30.1481C |
This paper presents our first experimental results on the photodegradation at 147 and 122 nm of hexamethylenetetramine (HMT). This molecule, suspected to be present on cometary grains, could be responsible for extended sources of CN and HCN in comets. We show that if HMT is quite resistant to direct photolysis under vacuum, interactions with water vapor photoproducts, which could happen in inner comae, lead to a much more efficient degradation with formation of HCN, NH3 and other N bearing molecules. Thus HMT could act as a parent or grand parent molecule for observed extended sources. However, additional source with greater degradation efficiency is certainly required to account observations in outer comae.
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Title: |
|
Are organic molecules produced by nebular Fischer-Tropsch processes preserved in comets? |
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Authors: |
|
|
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Journal: |
|
Advances in Space Research, Volume 30, Issue 6, p. 1469-1472. (AdSpR Homepage) |
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Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science B.V. All rights reserved. |
|
Bibliographic Code: |
|
2002AdSpR..30.1469L |
Chondritic porous interplanetary dust particles, thought to be of cometary origin, contain solid phases that were likely produced by gas-grain reactions in nebular environments. In the course of laboratory simulations addressed to reproduce under nebular conditions such distinctive mineralogies, simple organic molecules are formed through Fischer-Tropsch-type processes, suggesting that part of the organic volatiles in comets may have had a nebular origin. On the basis of these experiments, the relative abundances of homologous volatile hydrocarbons and the implications for the possible existence of thiols and sulfonic acids in comets are discussed.
|
Title: |
|
Biomolecules in the interstellar medium and in comets |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Space Science Division, MS 245-3, NASA Ames Research Center, Moffett Field CA 94035-1000, USA), AB(Space Science Division, MS 245-3, NASA Ames Research Center, Moffett Field CA 94035-1000, USA), AC(Space Science Division, MS 245-3, NASA Ames Research Center, Moffett Field CA 94035-1000, USA), AD(Space Science Division, MS 245-3, NASA Ames Research Center, Moffett Field CA 94035-1000, USA) |
|
Journal: |
|
Advances in Space Research, Volume 30, Issue 6, p. 1419-1431. (AdSpR Homepage) |
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Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science B.V. All rights reserved. |
|
Bibliographic Code: |
|
2002AdSpR..30.1419C |
We review recent studies of organic molecule formation in dense molecular clouds and in comets. We summarise the known organic inventories of molecular clouds and recent comets, particularly Hale-Bopp. The principal chemical formation pathways involving gas phase reactions, as well as formation by catalytic reactions on grain surfaces or through dust fragmentation, are identified for both dense clouds and cometary comae. The processes leading to organic molecules with known biological function, carbon chains, deuterium fractionation, HNC and S-bearing compounds are described. Observational searches for new interstellar organics are outlined and the connection between observed interstellar organics and those detected in comets Hale-Bopp and Hyakutake are discussed.
|
Title: |
|
Production of organic molecules in interstellar ices |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Raymond and Beverly Sackler Laboratory for Astrophysics
(SLA), |
|
Journal: |
|
Advances in Space Research, Volume 30, Issue 6, p. 1409-1417. (AdSpR Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science B.V. All rights reserved. |
|
Bibliographic Code: |
|
2002AdSpR..30.1409S |
Complex organic species are readily created when astrophysical ice analogs containing molecules like CO, H2CO and CH3OH are exposed to energetic processes like warm-up, UV photolysis and irradiation with energetic ions. We review the organic products that have been identified in such experiments and discuss the possible relevance of these results for the origin the organic molecules that are observed in comets and in the hot cores of star-forming regions.
|
Title: |
|
Neutral sodium tails in comets |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Osservatorio
Astronomico, vic. Osservatorio 5, 35122 Padova, Italy), AB(Osservatorio
Astronomico, vic. Osservatorio 5, 35122 Padova, Italy), AC(Osservatorio
Astronomico, vic. Osservatorio 5, 35122 Padova, Italy), AD(Osservatorio
Astronomico, vic. Osservatorio 5, 35122 |
|
Journal: |
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Advances in Space Research, Volume 29, Issue 8, p. 1187-1197. (AdSpR Homepage) |
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Publication Date: |
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00/2002 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
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(c) 2002 Elsevier Science B.V. All rights reserved. |
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Bibliographic Code: |
|
2002AdSpR..29.1187C |
Not Available
|
Title: |
|
The emission of gas and dust from comets |
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Authors: |
|
|
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Affiliation: |
|
AA(DLR Institute of Space Sensor Technology and Planetary
Exploration, Rutherfordstreet 2, 12489 |
|
Journal: |
|
Advances in Space Research, Volume 29, Issue 8, p. 1177-1186. (AdSpR Homepage) |
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Publication Date: |
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00/2002 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
|
(c) 2002 Elsevier Science B.V. All rights reserved. |
|
Bibliographic Code: |
|
2002AdSpR..29.1177B |
Not Available
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Title: |
|
Chemistry of O(1D) atoms in the coma: implications for cometary missions |
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Authors: |
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|
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Affiliation: |
|
AA(Space Physics Laboratory, Vikram Sarabhai Space Centre,
|
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Journal: |
|
Advances in Space Research, Volume 29, Issue 5, p. 745-750. (AdSpR Homepage) |
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Publication Date: |
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00/2002 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
|
(c) 2002 Elsevier Science B.V. All rights reserved. |
|
Bibliographic Code: |
|
2002AdSpR..29..745B |
The forbidden red oxygen lines at 6300 and 6364 Å, which results due to 1D->3P transition, provide an important diagnostic tool in the study of comets. These lines cannot be produced by resonance fluorescence excitation of the ground-state oxygen atom, and therefore are mainly produced due to dissociation of H2O and other O-containing species in comets (e.g., OH, CO, CO2, H2CO etc.) by photon and electron impact and in other collision reactions. Since the lifetime of 1D state is quite long (~110 sec) collisional de-excitation processes are important. We have used a coupled chemistry-transport model in conjunction with an efficient emission production code to study the chemistry of O(1D) atoms and the production of OI 6300 Å emission in comets. The model calculations are made for comet 46P/Wirtanen: the target of the ROSETTA mission. It is found that in the inner coma the density profile of O(1D) is controlled dominantly by the H2O. The model predicts ~300 R of OI 6300 A brightness on comet Wirtanen.
|
Title: |
|
Dynamics of cometary fragments. The case of comet 46P/Wirtanen |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Laboratoire de Planétologie de Grenoble, Bâtiment D de Physique, BP 53, F-38041 Grenoble Cedex 9, France), AB(Laboratoire de Planétologie de Grenoble, Bâtiment D de Physique, BP 53, F-38041 Grenoble Cedex 9, France) |
|
Journal: |
|
Advances in Space Research, Volume 29, Issue 5, p. 735-743. (AdSpR Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science B.V. All rights reserved. |
|
Bibliographic Code: |
|
2002AdSpR..29..735D |
Based on a dynamical model for the evolution of icy cometary fragments developed for comet C/1996 B2 Hyakutake, we investigate the sensitivity to the initial conditions of trajectories of hypothetic fragments close to the nucleus of comet 46P/Wirtanen. We performed Monte-Carlo simulations in order to test the dependence of the trajectories on initial position, on the orientation and the absolute value of the velocity vector. Due to the differential effect of the non-gravitational forces, a strong assymetry is found between the day side and the night side hemisphere. The possible ejection of fragments due to the rotation of the nucleus is discussed.
|
Title: |
|
A model of the activity of comet wild 2 |
|
Authors: |
|
|
|
Affiliation: |
|
AA(CNR-IAS,
Area di Ricerca di Tor Vergata, Via del Fosso del Cavaliere, I-00133 Rome,
Italy) |
|
Journal: |
|
Advances in Space Research, Volume 29, Issue 5, p. 709-714. (AdSpR Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science B.V. All rights reserved. |
|
Bibliographic Code: |
|
2002AdSpR..29..709C |
A numerical model of the thermal evolution and chemical differentiation of cometary nuclei was developed to help in the preparation of future comet missions. To better describe the microstructure of cometary matter we modified the way in which bulk thermal conductivity is expressed. The matter is now described as an aggregate of grains, formed by a refractory core and an ice mantle. In this way the evolution of the microstructure due to various physical processes, such as sintering, can be better simulated. With this kind of formulation, bulk conductivity could be very low, orders of magnitude lower than in our previous versions of the model. In order to test this expression and its consequences, we present here a simulation of the thermal evolution of comet Wild 2, the target of the STARDUST mission. We can see that a much lower conductivity changes the internal stratigraphy and the flux of low volatile gases, but does not affect surface properties and consequently water and dust fluxes.
|
Title: |
|
Laboratory studies of gas-dust jet formation on cometary nucleus surface |
|
Authors: |
|
|
|
Affiliation: |
|
AA( |
|
Journal: |
|
Advances in Space Research, Volume 29, Issue 5, p. 705-708. (AdSpR Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science B.V. All rights reserved. |
|
Bibliographic Code: |
|
2002AdSpR..29..705I |
Gas-dust jet formation in comets was simulated in laboratory experiments. Cometary nucleus models from water ice including solid carbon dioxide, solid acetone, other similar solid inhomogeneous impurities and dust particles were irradiated by light at high vacuum and at low temperatures. The sublimation rate, the temperature of the samples, and the mass-spectra of the gas emission from the samples were studied. The results of the experiments show that gas-dust jets from the surface of cometary nucleus models can form under certain condition.
|
Title: |
|
Influence of porosity on the thermal behaviour of comet surfaces |
|
Authors: |
|
|
|
Affiliation: |
|
AA(DLR Institut für Raumsimulation, 51170 |
|
Journal: |
|
Advances in Space Research, Volume 29, Issue 5, p. 691-704. (AdSpR Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science B.V. All rights reserved. |
|
Bibliographic Code: |
|
2002AdSpR..29..691M |
Comet nuclei are assumed to be of porous structure. A consequence of the porosity of sublimating matter is that sublimation will take place also at ``internal'' surfaces and not only at the outer surface. This considerably modifies the thermal and sublimation behaviour. The surface material will be cooler if compared to a non-porous surface while the temperature gradients increase. The resulting comet diurnal and depth variations of temperature and outgassing properties are described in some detail in their dependence on heliocentric distance for different porosities, pore radii and heat conductivities for a model nucleus on the orbit of comet 46P/Wirtanen. The results are compared to astronomically observed properties of this comet. Based on that, ``most appropriated'' numerical values or ranges of parameters which can be used to characterize the properties of comet 46P/Wirtanen are identified.
|
Title: |
|
Doubly Ionized Carbon Observed in the Plasma Tail of Comet Kudo-Fujikawa |
|
Authors: |
|
Povich, Matthew S.; Raymond, John C.; Jones, Geraint H.; Uzzo, Michael; Ko, Yuan-Kuen; Feldman, Paul D.; Smith, Peter L.; Marsden, Brian G.; Woods, Thomas N. |
|
Affiliation: |
|
AA(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.), AB(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.), AC(Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, USA.), AD(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.), AE(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.), AF(Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218-2686, USA.), AG(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.), AH(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.), AI(University of Colorado, Laboratory for Atmospheric and Space Physics, 1234 Innovation Drive, Boulder, CO 80303, USA.) |
|
Journal: |
|
Science, Volume 302, Issue 5652, pp. 1949-1952 (2003). |
|
Publication Date: |
|
12/2003 |
|
Category: |
|
PLANET SCI |
|
Origin: |
|
SCIENCE |
|
Abstract Copyright: |
|
(c) 2003: Science |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2003Sci...302.1949P |
Comet C/2002 X5 (Kudo-Fujikawa) was observed near its perihelion of 0.19 astronomical unit by the Ultraviolet Coronagraph Spectrometer aboard the Solar and Heliospheric Observatory spacecraft. Images of the comet reconstructed from high-resolution spectra reveal a quasi-spherical cloud of neutral hydrogen and a variable tail of C+ and C2+ that disconnects from the comet and subsequently regenerates. The high abundance of C2+ and C+, at least 24% relative to water, cannot be explained by photodissociation of carbon monoxide and is instead attributed to the evaporation and subsequent photoionization of atomic carbon from organic refractory compounds present in the cometary dust grains. This result serves to strengthen the connection between comets and the material from which the Solar System formed.
|
Title: |
|
Spectroscopic Observations of |
|
Authors: |
|
Furusho, Reiko; Kawakita, Hideyo; Fujii, Mitsugu; Kinugasa, Kenzo; Yamamuro, Tomoyasu; Takeyama, Norihide |
|
Affiliation: |
|
AA(Japan Science and Technology Corporationfurshork@cc.nao.ac.jp), AB(Gunma Astronomical Observatory), AC(4500 Kurosaki, Tamashima, Okayama 713-8126), AD(Gunma Astronomical Observatory), AE(Genesia Corporation), AF(Genesia Corporation) |
|
Journal: |
|
Publications of the Astronomical Society of |
|
Publication Date: |
|
12/2003 |
|
Origin: |
|
PASJ |
|
Keywords: |
|
comets: general -- comets: individual [C/2001 A2 (LINEAR)] -- solar system: formation |
|
Abstract Copyright: |
|
(c) 2003: Astronomical Society of |
|
Bibliographic Code: |
|
2003PASJ...55.1153F |
Low-dispersion spectroscopic observations of C/2001A2 (LINEAR) were performed before and after its perihelion passage. C/2001A2 (LINEAR) showed the first outburst late in 2001 March, and its visual magnitude increased by more than 5mag. In addition to this outburst, three outbursts were recognized around the perihelion passage of the comet. These outbursts are thought to be associated with splitting events of the cometary nucleus. Our first observation was performed on 2001 April4, during the first outburst. After its perihelion passage, its spectra were obtained on July2, with its normal activity, and July12, during an outburst. We determined the gas-to-dust ratios [Q(H2O) / Afρ], as well as gas production rate ratios of CN, C2, and NH2 relative to water [Q(X) / Q(H2O})] for each observation. Obtained gas-to-dust ratios (26.4-26.7) showed that C/LINEAR was a gas-rich comet. Our results showed that there were no significant changes in the gas-to-dust ratio and gas production rate ratios during 3 months around perihelion passage. In comparison with other comets, there were no significant differences in the chemical composition for C/2001A2 (LINEAR).
|
Title: |
|
Hcn and Hnc in Comets C/2000 Wm1 (Linear) and C/2002 C1 (Ikeya-Zhang) |
|
Authors: |
|
Irvine, William M.; Bergman, Per; Lowe, Thomas B.; Matthews, Henry; McGonagle, Douglas; Nummelin, Albert; Owen, Toby |
|
Affiliation: |
|
AA(Department of Astronomy and Five College Radio Astronomy Observatory, University of Massachusetts, Amherst, MA, U.S.A. (author for correspondence, e-mail: irvine@fcrao1.astro.umass.edu, Fax: 413 545 4223)), AB(Onsala Space Observatory, Chalmers University of Technology, Onsala, Sweden), AC(Joint Astronomy Centre, Hilo, U.S.A.), AD(Joint Astronomy Centre, Hilo, U.S.A. and Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria, Canada), AE(Department of Astronomy and Five College Radio Astronomy Observatory, University of Massachusetts, Amherst, MA, U.S.A.), AF(Department of Electrical and Computer Engineering, Chalmers Lindholmen University College, Gothenburg, Sweden), AG(Institute for Astronomy, University of Hawaii, Honolulu, U.S.A.) |
|
Journal: |
|
Origins of Life and Evolution of the Biosphere, v. 33, Issue 6, p. 609-619 (2003). |
|
Publication Date: |
|
12/2003 |
|
Origin: |
|
KLUWER |
|
Abstract Copyright: |
|
(c) 2003 Kluwer Academic Publishers |
|
Bibliographic Code: |
|
2003OLEB...33..609I |
Comets have been suggested as a possibly significant source of organic molecules to the early Earth. Hydrogen cyanide (HCN) is important in models of prebiotic chemistry, but may be difficult to form in the early terrestrial environment, while hydrogen isocyanide (HNC) is a `classical' tracer of interstellar ion-molecule chemistry. We have observed both HCN and HNC in 2 recent comets, bringing the number of comets with published measurements of the HNC/HCN abundance ratio to 6. The HNC/HCN ratio in comet Ikeya-Zhang appears to increase with decreasing heliocentric distance, as was previously observed for comet Hale-Bopp, indicating that the HNC is produced at least in part by processes in the cometary coma (atmosphere) and is not simply a constituent of the nuclear ices. Both comets C/2000 WM1 (Linear) and C/2002 C1 (Ikeya-Zhang) exhibit values of the HNC/HCN ratio that appear to be too large (~0.09-0.19) to be matched by current models of coma chemistry. Cometary HNC may be a photodissociation product of organic grains or large organic polymers stored in the nucleus. We have also set a limit on the emission from the NO radical in comet WM1.
|
Title: |
|
The variation of short-period comet size and decay rate with perihelion distance |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Department of Physics and Astronomy, The University, |
|
Journal: |
|
Monthly Notices of the Royal Astronomical Society, Volume 346, Issue 2, pp. 584-592. (MNRAS Homepage) |
|
Publication Date: |
|
12/2003 |
|
Origin: |
|
MNRAS |
|
Abstract Copyright: |
|
(c) 2003 RAS |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2003MNRAS.346..584H |
Out of over 200 known short-period comets, we analyse a self-consistent list of 105 comets which have accurately estimated nuclei radii. It is found that both the median size and the size distribution index of these comets vary as a function of the perihelion distance, q, of the cometary orbit. A value of q~ 2.7 au divides the comets into an outer solar system group which are hardly affected by decay, and an inner solar system group which are decaying quickly. It is estimated that 10, 20 and 30 per cent of the 105 comets will have decayed away after 1000, 2000 and 3000 yr, respectively.
|
Title: |
|
The effect of amplification of sublimation from an active region on the surface of a rotating cometary nucleus |
|
Authors: |
|
|
|
Journal: |
|
Kinematika i
Fizika Nebesnykh Tel, vol. 19, no. 6, p. 514-522 |
|
Publication Date: |
|
12/2003 |
|
Origin: |
|
KFNT |
|
Language: |
|
Ukrainian |
|
Bibliographic Code: |
|
2003KFNT...19..514I |
The inhomogeneity of cometary nuclei emerges in the fact that there are some active areas on the surface of a cometary nucleus which are sources of observed gas-and-dust jets. The active regions of a cometary nucleus are formed by local disruption of the dust layer, though a possible mechanism of this disruption are not clear. We investigated the temperature distribution on the icy bottom and dust walls of the crater on the surface of a cometary nucleus and the effect of amplification of sublimation due to the concentration of the solar radiation by the conical hole depending on its geometrical parameters and on the nucleus rotation.
|
Title: |
|
Peculiarities of the motion of sizable dust grains in cometary atmospheres |
|
Authors: |
|
|
|
Journal: |
|
Kinematika i
Fizika Nebesnykh Tel, vol. 19, no. 6, p. 501-513 |
|
Publication Date: |
|
12/2003 |
|
Origin: |
|
KFNT |
|
Language: |
|
Russian |
|
Bibliographic Code: |
|
2003KFNT...19..501A |
We performed a simulation of
trajectories of sizable dust grains with consideration for two specific points
found on phase plane of cm-sized dust particles in our previous investigation
(Andrienko D. A.,
|
Title: |
|
On the Solar EUV Deposition in the Inner Comae of Comets with Large Gas Production Rates |
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Authors: |
|
|
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Journal: |
|
Geophysical Research Letters, Volume 30, Issue 24, pp. PLA 2-1, CiteID 2244, DOI 10.1029/2003GL018495 (GeoRL Homepage) |
|
Publication Date: |
|
12/2003 |
|
Origin: |
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AGU |
|
AGU Keywords: |
|
Atmospheric Composition and Structure: Airglow and aurora, Planetology: Comets and Small Bodies: Atmospheres-composition and chemistry, Planetology: Comets and Small Bodies: Ionospheres-composition and chemistry, Planetology: Solar System Objects: Comets |
|
Abstract Copyright: |
|
(c) 2003: American Geophysical |
|
Bibliographic Code: |
|
2003GeoRL..30xPLA2B |
In this letter we have made a comparative study of degradation of solar EUV radiation and EUV-generated photoelectrons in the inner comae of comets having different gas production rates, Q, with values 1 × 1028, 7 × 1029, 1 × 1031, and 1 × 1032 s-1. We found that in higher-Q comets the radial profile of H2O+ photo-production rate depicts a double-peak structure and that the differences in sunward and anti-sunward photoionization rates are pronounced. We show that photoelectron impact ionization is an order of magnitude larger than photoionization rate near the lower photoionization peak in comets with Q > ~1 × 1031 s-1. The present study reveals the importance of photoelectrons relative to solar EUV as the ionization source in the inner coma of high-Q comets.
|
Title: |
|
Activity on the surface of the nucleus of comet 46P/Wirtanen |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Laboratoire
d'Astrophysique de Marseille, BP 8, 13376 Marseille Cedex 12, France) |
|
Journal: |
|
Astronomy and Astrophysics, v.412, p.879-891 (2003) (A&A Homepage) |
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Publication Date: |
|
12/2003 |
|
Origin: |
|
A&A |
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A&A Keywords: |
|
comets: individual: 46P/Wirtanen |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2003A&A...412..879G |
We present a thermal model of the nucleus of comet 46P/Wirtanen, constrained by the temporal variations of the water production rate, in order to understand the activity on its surface. We consider a spherical nucleus with a macroscopic mosaic of small and numerous active and inactive regions. At heliocentric distances rh > 1.5 AU, the active regions represent 5-15% of the surface. At ~ 1.5 AU, a rapid increase takes place and the active fraction reaches 70 to 100% in about 10 days, and then remains approximately constant up to perihelion where QH_2O=1.3+/-0.3*E28 molecule s-1. Post-perihelion, this fraction returns to ~ 10%. The model is consistent with a geometric albedo <=0.06. A refractory crust likely forms post-perihelion and can explain the variations of the activity over an orbit. Finally, we derived an erosion of ~ 0.5 m per revolution and a remaining lifetime for the nucleus of several hundred revolutions.
|
Title: |
|
UV-photoprocessing of interstellar ice analogs: New infrared spectroscopic results |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Raymond and Beverly Sackler Laboratory for Astrophysics, Leiden Observatory, 2300 RA Leiden, The Netherlands; Institut d'Astrophysique Spatiale, UMR 8617, Bât. 121, Campus Paris XI, 91405 Orsay, France), AB(Raymond and Beverly Sackler Laboratory for Astrophysics, Leiden Observatory, 2300 RA Leiden, The Netherlands) |
|
Journal: |
|
Astronomy and Astrophysics, v.412, p.121-132 (2003) (A&A Homepage) |
|
Publication Date: |
|
12/2003 |
|
Origin: |
|
A&A |
|
A&A Keywords: |
|
infrared: ISM, ISM: lines and bands, methods: laboratory, ultraviolet: ISM, ISM: dust, extinction |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2003A&A...412..121M |
We simulate experimentally the physical conditions present in dense clouds by means of a high vacuum experimental setup at low temperature T ~ 12 K. The accretion and photoprocessing of ices on grain surfaces is simulated in the following way: an ice layer with composition analogous to that of interstellar ices is deposited on a substrate window, while being irradiated by ultraviolet (UV) photons. Subsequently the sample is slowly warmed up to room temperature; a residue remains containing the most refractory products of photo- and thermal processing. In this paper we report on the Fourier transform-infrared (FT-IR) spectroscopy of the refractory organic material formed under a wide variety of initial conditions (ice composition, UV spectrum, UV dose and sample temperature). The refractory products obtained in these experiments are identified and the corresponding efficiencies of formation are given. The first evidence for carboxylic acid salts as part of the refractory products is shown. The features in the IR spectrum of the refractory material are attributed to hexamethylenetetramine (HMT, [(CH2)6N4]), ammonium salts of carboxylic acids [(R-COO-)(NH+4)], amides [H2NC(=O)-R], esters [R-C(=O)-O-R'] and species related to polyoxymethylene (POM, [(-CH2O-)n]). Furthermore, evidence is presented for the formation of HMT at room temperature, and the important role of H2O ice as a catalyst for the formation of complex organic molecules. These species might also be present in the interstellar medium (ISM) and form part of comets. Ongoing and future cometary missions, such as Stardust and Rosetta, will allow a comparison with the laboratory results, providing new insight into the physico-chemical conditions present during the formation of our solar system.
|
Title: |
|
Young Meteor Swarms Near the Sun: |
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Authors: |
|
|
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Affiliation: |
|
AA(Astronomical Observatory, |
|
Journal: |
|
Solar System Research, v. 37, Issue 6, p. 506-518 (2003). |
|
Publication Date: |
|
11/2003 |
|
Origin: |
|
KLUWER |
|
Abstract Copyright: |
|
(c) 2003 Kluwer Academic Publishers |
|
Bibliographic Code: |
|
2003SoSyR..37..506G |
We examine the hypothesis about the formation of meteor streams near the Sun. Families of short-perihelion orbit comets, many of which pass just a few radii from the solar surface at perihelion and have high dust production efficiencies, are assumed to be candidates for the parent bodies of these meteor streams. Our statistical analysis of orbital and kinematic parameters for short-perihelion meteoric particles recorded at the Earth and comets from the Kreutz family and the Marsden, Kracht, and Meyer groups led us to certain conclusions regarding the proposed hypothesis. We found a correlation between the ecliptic longitude of perihelion for comet and meteor orbits and the perihelion distance. This correlation may be suggestive of either a genetic connection between the objects of these two classes or the result of an as yet unknown mechanism that equally acts on short-perihelion comet and meteor orbits. A reliable conclusion about this genetic connection can be reached for the meteors that belong to the Arietids stream and the Marsden comet group.
|
Title: |
|
The absolute magnitude distribution of trans-Neptunian objects |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Department of Physics and Astronomy, The University, |
|
Journal: |
|
Monthly Notices of the Royal Astronomical Society, Volume 345, Issue 3, pp. 981-984. (MNRAS Homepage) |
|
Publication Date: |
|
11/2003 |
|
Origin: |
|
MNRAS |
|
Abstract Copyright: |
|
(c) 2003 RAS |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2003MNRAS.345..981H |
It is shown that the known trans-Neptunian objects (TNOs) have an absolute magnitude distribution index that increases as a function of orbital perihelion distance. In no perihelion range is the TNO index the same as that found for known short-period comets. However, the fact that the median diameters of the known members of these two populations (220 and 2.9 km respectively) differ by a factor of about 75 means that very small TNOs and short-period comets might still be related.
|
Title: |
|
Dust coma of Comet C/1999 S4 (LINEAR): imaging polarimetry during nucleus disruption |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Service
d'Aéronomie/CNRS/IPSL, BP 3, Verrières le Buisson, 91371 France; ), AB(Université Paris 6 /Service d'Aéronomie/IPSL, Verrières le
Buisson, 91371 France) |
|
Journal: |
|
Icarus, Volume 166, Issue 1, p. 188-194. (Icarus Homepage) |
|
Publication Date: |
|
11/2003 |
|
Origin: |
|
ELSEVIER |
|
Keywords: |
|
Comets, Polarization, Light scattering |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2003Icar..166..188H |
Imaging and polarimetry of Comet C/1999 S4 (LINEAR) during its disruption provide information about the physical properties of the scattering dust particles, and some insight into the structure of the nucleus. A significant decrease in the brightness was noticed, together with a drastic change in the shape of the dust coma. The whole-coma polarization increased, which was typical of a comet with a near 27 percent maximum in polarization, the increase being comparable to previous observations for comets suffering a limited fragmentation. An important gradient in the intensity on the solar side corresponds to the ejected material. The degree of polarization in this region is higher than generally observed in jets and it increases with time as the nucleus (or its fragments) breaks up and ejects relatively large and compact particles. In the surrounding coma, these large particles are fragmented on short time-scales, indicated by the decrease of polarization. These results suggest that the fragile nucleus was not, as far as the physical properties of the dust are concerned, differentiated, and that it was possibly built of primordial cometesimals originating from the same formation region.
|
Title: |
|
Spectroscopy of Comet Hale-Bopp in the infrared |
|
Authors: |
|
Brooke, T. Y.; Weaver, H. A.; Chin, G.; Bockelée-Morvan, D.; Kim, S. J.; Xu, L.-H. |
|
Affiliation: |
|
AA(Jet Propulsion Laboratory, MS 169-237, 4800 Oak Grove Drive, Pasadena, CA 91109, USA; tyb@astro.caltech.edu), AB(Center for Astrophysical Sciences, Department of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA), AC(Laboratory for Extraterrestrial Physics, Planetary Systems Branch, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA), AD(Observatoire de Paris-Meudon, 5 Place Jules Janssen, F-92195 Meudon, France), AE(Institute of Natural Sciences, Kyunghee University, Yongin, Kyunggido 449-701, South Korea), AF(Department of Physical Sciences, University of New Brunswick, Saint John, NB, Canada) |
|
Journal: |
|
Icarus, Volume 166, Issue 1, p. 167-187. (Icarus Homepage) |
|
Publication Date: |
|
11/2003 |
|
Origin: |
|
ELSEVIER |
|
Keywords: |
|
Hale-Bopp, composition, Infrared observations, Spectroscopy |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2003Icar..166..167B |
High resolution infrared spectra of Comet C/1995 O1 (Hale-Bopp) were obtained during 2-5 March 1997 UT from the NASA Infrared Telescope Facility on Mauna Kea, Hawaii, when the comet was at r~1.0 AU from the Sun pre-perihelion. Emission lines of CH4, C2H6, HCN, C2H2, CH3OH, H2O, CO, and OH were detected. The rotational temperature of CH4 in the inner coma was Trot=110+/-20 K. Spatial profiles of CH4, C2H6, and H2O were consistent with release solely from the nucleus. The centroid of the CO emission was offset from that of the dust continuum and H2O. Spatial profiles of the CO lines were much broader than those of the other molecules and asymmetric. We estimate the CO production rate using a simplified outflow model: constant, symmetric outflow from the peak position. A model of the excitation of CO that includes optical depth effects using an escape probability method is presented. Optical depth effects are not sufficient to explain the broad spatial extent. Using a parent+extended-source model, the broad extent of the CO lines can be explained by CO being produced mostly (~90% on 5 March) from an extended source in the coma. The CO rotational temperature was near 100 K. Abundances relative to H2O (in percent) were 1.1+/-0.3 (CH4), 0.39+/-0.10 (C2H6), 0.18+/-0.04 (HCN), 0.17+/-0.04 (C2H2), 1.7+/-0.5 (CH3OH), and 37-41 (CO, parent+extended source). These are roughly comparable to those obtained for other long-period comets also observed in the infrared, though CO appears to vary.
|
Title: |
|
The rotational structure of the B-X system of sulfur dimers in the spectra of Comet Hyakutake (C/1996 B2) |
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Authors: |
|
Kim, Sang J.; A'Hearn, M. F.; Wellnitz, D. D.; Meier, R.; Lee, Y. S. |
|
Affiliation: |
|
AA(Department of Astronomy and Space Science, Kyung Hee University, Suwon 449-701, South Korea; sjkim1@khu.ac.kr), AB(Astronomy Program, University of Maryland, College Park, MD 20742, USA), AC(Astronomy Program, University of Maryland, College Park, MD 20742, USA), AD(Hallwylstr. 4, Aarau 5000, Switzerland), AE(Department of Chemistry and Department of Astronomy, Kyung Hee University, Suwon 449-701, South Korea) |
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Journal: |
|
Icarus, Volume 166, Issue 1, p. 157-166. (Icarus Homepage) |
|
Publication Date: |
|
11/2003 |
|
Origin: |
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ELSEVIER |
|
Keywords: |
|
Comet, Coma, Atmosphere, Molecule, Fluorescence, Radiative transfer |
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DOI: |
|
|
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Bibliographic Code: |
|
2003Icar..166..157K |
We have constructed line-by-line fluorescence models for the ro-vibrational bands of the B-X system of sulfur dimers (S2). For the first time the detailed rotational lines of the bands are clearly resolved in the high-resolution echelle spectra of Comet Hyakutake (C/1996 B2), which were obtained at the Kitt Peak 4-m telescope on 26.4 March 1996 (UT). In order to construct satisfactory band models of the B-X system, we first compared the models to laboratory spectra available in literature, and then compared the models including Swings effects to the high-resolution spectra of Hyakutake. From the model fits, we derived a rotational temperature of 70+/-10 K, which should represent a temperature of a coma region close to the nucleus, where most of the S2 emissions originate. We present previously proposed scenarios for the origin of S2 in cometary comae, and compare them with our spectral analysis.
|
Title: |
|
Dust impacts at Comet P/Borrelly |
|
Authors: |
|
Tsurutani, B. T.; Clay, D. R.; Zhang, L. D.; Dasgupta, B.; Brinza, D.; Henry, M.; Mendis, A.; Moses, S.; Glassmeier, K.-H.; Musmann, G.; Richter, I. |
|
Journal: |
|
Geophysical Research Letters, Volume 30, Issue 22, pp. SSC 1-1, CiteID 2134, DOI 10.1029/2003GL017580 (GeoRL Homepage) |
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Publication Date: |
|
11/2003 |
|
Origin: |
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AGU |
|
AGU Keywords: |
|
Planetology: Comets and Small Bodies: Dust, Planetology: Comets and Small Bodies: Impact phenomena |
|
Abstract Copyright: |
|
(c) 2003: American Geophysical |
|
Bibliographic Code: |
|
2003GeoRL..30vSSC1T |
The NASA DS1 spacecraft flew past comet P/Borrelly on September 22, 2001, on the sunward side of the comet. Dust impacts were detected by sharp increases (or decreases) in electric fields measured by the plasma wave dipole antennae. Electric pulses from as small as 0.014 Vm-1 to saturation (~+/-0.8 Vm-1) were detected. Pulse overshoots were noted in the largest electric pulses. No simultaneous dc magnetic signatures >1 nT were detected in the magnetometer data. Assuming that cometary dust grains propagating in the sunward direction were decelerated by solar radiation pressure, arguments are made that the size of the earliest dust particles detected were probably ~0.4 μm in radius. Elaboration of the characteristics of these electric pulses and pulse overshoots and their interpretations will be reserved for a subsequent work.
|
Title: |
|
Numerical study on the spatial extent of interaction region surrounding comet nucleus - Ion pick-up process |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Department of Geophysics, |
|
Journal: |
|
Earth, Planets and Space, Volume 55, p. 705-711. (EP&S Homepage) |
|
Publication Date: |
|
11/2003 |
|
Origin: |
|
TERRAPUB |
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Bibliographic Code: |
|
2003EP&S...55..705K |
The observations made by Sakigake revealed the asymmetric distribution of the interaction region of Halley's comet, and the center of the interaction region was shifted toward the post-encounter side on the spacecraft trajectory. Oya (1993) proposed the model that this asymmetric distribution is explained by the field aligned motion of picked up ions. Based on this model, we examined spatial and time scale of field aligned motion of cometary ions in the ion pick-up process by using numerical experiments and the shift of the interaction region is estimated. In the simulation results, it was shown that the braking process of the field aligned motion of picked up ions are understood by the wave particle interaction through the excitation of the MHD wave and pitch angle scattering caused by the turbulent magnetic field, and spatial scale of field aligned motion of cometary ion was estimated to 1.5 İ 106 km. This result suggests that observed asymmetrical distribution of the interaction region of the comet is formed by the motion of picked up ions toward the field aligned direction until their merging into the solar wind, as it was proposed by Oya (1993).
|
Title: |
|
Erosion Model for the Sungrazing Comets Observed with the Solar and Heliospheric Observatory |
|
Authors: |
|
|
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Affiliation: |
|
AA(Jet Propulsion Laboratory, California Institute of Technology,
|
|
Journal: |
|
The Astrophysical Journal, Volume 597, Issue 2, pp. 1237-1265. (ApJ Homepage) |
|
Publication Date: |
|
11/2003 |
|
Origin: |
|
UCP |
|
ApJ Keywords: |
|
Comets: General, Methods: Data Analysis |
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Abstract Copyright: |
|
(c) 2003: The American Astronomical Society |
|
DOI: |
|
|
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Bibliographic Code: |
|
2003ApJ...597.1237S |
The objectives of this study are
to model and interpret quantitatively the brightness variations of 27 Solar and
Heliospheric Observatory (SOHO) sungrazers. The light curves, published by Uzzo
et al. and by Biesecker et al., are shown to provide information on a proposed
erosion process, which consists of continuous, progressive bulk fragmentation
and sublimation of these minicomets on their approach to the Sun. The erosion
rate and the time of peak signal are determined primarily by an effective
latent energy of erosion (analogous to a sublimation heat), which is found to
have a bimodal distribution with sharp peaks near 34,000-35,000 and
40,000-41,000 cal mol-1 for the main components of the 27 objects.
Their derived initial diameters are between 17 and 200 m. With the given range
of erosion energies, a sungrazer that is to survive its return to the Sun needs
to be more than 1-1.4 km in diameter, depending on its perihelion distance. The
shape of the light curves at heliocentric distances smaller than 7 Rsolar
is interpreted to indicate the existence of fairly sizable, but unresolved,
close companions, which appear to have split off from their parent bodies
shortly before, if not during, observation. All subfragments that survived
longer than the main components had erosion energies significantly higher than
the average, between 45,000 and nearly 90,000 cal mol-1. There is
also evidence for subfragments with erosion energies lower than 34,000 cal mol-1.
Because the erosion process is believed to be dominated by continual
fragmentation, the existence of such subfragments should not be surprising. The
brightness of the
|
Title: |
|
Dust tail of the distant comet C/1999 J2 (Skiff) |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Main Astronomical Observatory, Ukrainian Academy of Sciences, Kyiv, Ukraine korsun@mao.kiev.ua; Isaac Newton Institute of Chile, Kiev Branch, Russia), AB(Main Astronomical Observatory, Ukrainian Academy of Sciences, Kyiv, Ukraine) |
|
Journal: |
|
Astronomy and Astrophysics, v.410, p.1029-1037 (2003) (A&A Homepage) |
|
Publication Date: |
|
11/2003 |
|
Origin: |
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A&A |
|
A&A Keywords: |
|
comets: individual: C/1999 J2 (Skiff) |
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DOI: |
|
|
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Bibliographic Code: |
|
2003A&A...410.1029K |
CCD observations of comet C/1999
J2 (Skiff) were made at the Pik Terskol Observatory on September 15, 1999. The
2-m telescope equipped with the two-channel focal reducer of the
Max-Plank-Institute for Aeronomy was used to study the cometary environment. In
spite of the large heliocentric distance, 7.24 AU, a straight dust tail with
fairly well defined boundaries was recorded. These data provide an opportunity
to study the peculiarity of dust, that is not driven by water vapor. To fit the
dust tail, a
|
Title: |
|
Methane in Oort cloud comets |
|
Authors: |
|
Gibb, E. L.; Mumma, M. J.; dello Russo, N.; Disanti, M. A.; Magee-Sauer, K. |
|
Affiliation: |
|
AA(NAS-NRC, Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center Code 690, 20771, Greenbelt, MD, USA), AB(Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center Code 690, 20771, Greenbelt, MD, USA), AC(Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center Code 690, 20771, Greenbelt, MD, USA), AD(Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center Code 690, 20771, Greenbelt, MD, USA), AE(Department of Chemistry and Physics, Rowan University, 08028, Glassboro, NJ, USA) |
|
Journal: |
|
Icarus, Volume 165, Issue 2, p. 391-406. (Icarus Homepage) |
|
Publication Date: |
|
10/2003 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2003 Elsevier ( |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2003Icar..165..391G |
We detected CH4 in
eight Oort cloud comets using high-dispersion (λ/Δλ~2×104) infrared spectra
acquired with CSHELL at NASA's IRTF and NIRSPEC at the W.M. Keck Observatory.
The observed comets were C/1995 O1 (Hale-Bopp), C/1996 B2 (Hyakutake), C/1999
H1 (Lee), C/1999 T1 (McNaught-Hartley), C/1999 S4 (LINEAR), C/2000 WM1
(LINEAR), C/2001 A2 (LINEAR), and 153/P Ikeya-Zhang (C/2002 C1). We detected
the R0 and R1 lines of the ν3 vibrational band of CH4
near 3.3 μm in each comet, with the exception of McNaught-Hartley where only
the R0 line was measured. In order to obtain production rates, a fluorescence
model has been developed for this band of CH4. We report /g-factors
for the R0 and R1 transitions at several rotational temperatures typically
found in comet comae and relevant to our observations. Using /g-factors
appropriate to Trot as determined from
|
Title: |
|
Facile Generation and Storage of Polycyclic Aromatic Hydrocarbon Ions in Astrophysical Ices |
|
Authors: |
|
|
|
Affiliation: |
|
AA(NASA Ames Research Center, MS 245-6, Moffett Field, CA 94035-1000 .; Institute for Physical Sciences and Technology, University of Maryland, College Park, MD 20742; gudipati@ipst.umd.edu.; Also associated with the Institut für Physikalische Chemie, Universität zu Köln, Köln, Germany.), AB(NASA Ames Research Center, MS 245-6, Moffett Field, CA 94035-1000 .) |
|
Journal: |
|
The Astrophysical Journal, Volume 596, Issue 2, pp. L195-L198. (ApJ Homepage) |
|
Publication Date: |
|
10/2003 |
|
Origin: |
|
UCP |
|
ApJ Keywords: |
|
Astrochemistry, Comets: General, ISM: Dust, Extinction, ISM: Molecules, Methods: Laboratory, Molecular Processes |
|
Abstract Copyright: |
|
(c) 2003: The American Astronomical Society |
|
DOI: |
|
|
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Bibliographic Code: |
|
2003ApJ...596L.195G |
In situ ultraviolet-visible absorption and emission studies of vacuum ultraviolet (VUV) irradiated water-rich, cosmic ice analogs containing polycyclic aromatic hydrocarbons (PAHs) are described. VUV irradiation of 12 K water ices containing the PAHs naphthalene (H2O/C10H8 = 200) and 4-methylpyrene (H2O/C17H12 > 500) readily converts the PAHs into their cation form (PAH+). Under these conditions, PAH photoionization is the predominant reaction. These ions are trapped and stored in the ices at temperatures between 10 and 50 K, a temperature domain common to ices throughout interstellar clouds and the solar system. Unlike the ~15% ionization typical after VUV irradiation of PAHs isolated in rare-gas matrices, in water ice, PAH photoionization and storage proceed efficiently and almost quantitatively with a greater than 70% ionization yield. As the temperature is increased from 50 to 150 K, the PAH ion bands slowly diminish as the PAH ions ultimately react to form more complex organic species involving the water host. The chemical, spectroscopic, and physical properties of these ion-rich ices can be important in icy objects such as molecular clouds, comets, and planets. Several astrophysical applications are presented.
|
Title: |
|
Meeting report: Meteorites, meteors and comets |
|
Authors: |
|
|
|
Affiliation: |
|
AA(() is Director of the BAA Comet Section.;) |
|
Journal: |
|
Astronomy & Geophysics, Volume 44, Issue 5, pp. 5.31-5.32. |
|
Publication Date: |
|
10/2003 |
|
Origin: |
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A&G |
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DOI: |
|
|
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Bibliographic Code: |
|
2003A&G....44e..31S |
There are many areas in which professional and amateur co-operation brings benefits to both. Speakers at the RAS-BAA Pro-am discussion meeting on 10 May explored observational work on some of the debris in the solar system. The meeting concluded with a lecture given in memory of the noted amateur astronomer George Alcock. Jonathan Shanklin reports.
|
Title: |
|
Anomalous Nitrogen Isotope Ratio in Comets |
|
Authors: |
|
Arpigny, Claude; Jehin, Emmanuël; Manfroid, Jean; Hutsemékers, Damien; Schulz, Rita; Stüwe, J. A.; Zucconi, Jean-Marc; Ilyin, Ilya |
|
Affiliation: |
|
AA(Institut d'Astrophysique et de Géophysique, Sart-Tilman, Bâtiment B5c, B-4000 Liège, Belgium.), AB(European Southern Observatory, Casilla 19001, Santiago, Chile.), AC(Institut d'Astrophysique et de Géophysique, Sart-Tilman, Bâtiment B5c, B-4000 Liège, Belgium.), AD(Institut d'Astrophysique et de Géophysique, Sart-Tilman, Bâtiment B5c, B-4000 Liège, Belgium.), AE(ESA/RSSD, ESTEC, Post Office Box 299, NL-2200 AG Noordwijk, Netherlands.), AF(Leiden Observatory, NL-2300 RA Leiden, Netherlands.), AG(Observatoire de Besançon, F25010 Besançon Cedex, France.), AH(Astronomy Division, Post Office Box 3000, FIN 90014 University of Oulu, Finland.) |
|
Journal: |
|
Science, Volume 301, Issue 5639, pp. 1522-1525 (2003). |
|
Publication Date: |
|
09/2003 |
|
Category: |
|
PLANET SCI |
|
Origin: |
|
SCIENCE |
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Abstract Copyright: |
|
(c) 2003: Science |
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DOI: |
|
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Bibliographic Code: |
|
2003Sci...301.1522A |
High-resolution spectra of the CN B2 Σ+-X2 Σ+ (0,0) band at 390 nanometers yield isotopic ratios for comets C/1995 O1 (Hale-Bopp) and C/2000 WM1 (LINEAR) as follows: 165 +/- 40 and 115 +/- 20 for 12C/13C, 140 +/- 35 and 140 +/- 30 for 14N/15N. Our N isotopic measurements are lower than the terrestrial 14N/15N = 272 and the ratio for Hale-Bopp from measurements of HCN, the presumed parent species of CN. This isotopic anomaly suggests the existence of other parent(s) of CN, with an even lower N isotopic ratio. Organic compounds like those found in interplanetary dust particles are good candidates.
|
Title: |
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Shock surfing acceleration |
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Authors: |
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|
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Affiliation: |
|
AA(University of California, San Diego, Physics Department, 92093, La Jolla CA, USA), AB(University of California, San Diego, Physics Department, 92093, La Jolla CA, USA) |
|
Journal: |
|
Planetary and Space Science, Volume 51, Issue 11, p. 665-680. (P&SS Homepage) |
|
Publication Date: |
|
09/2003 |
|
Origin: |
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ELSEVIER |
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Bibliographic Code: |
|
2003P&SS...51..665S |
Analytical and numerical analysis identify shock surfing acceleration as an ideal pre-energization mechanism for the slow pick-up ions at quasiperpendicular shocks. After gaining sufficient energy by shock surfing, pick-up ions undergo diffusive acceleration to reach their observed energies. Energetic ions upstream of the cometary bow shock, acceleration of solar energetic particles by magnetosonic waves in corona, ion enhancement in interplanetary shocks, generation of anomalous cosmic rays from interstellar pick-up ions at the termination shock are some of the cases where shock surfing acceleration apply. Inclusion of the lower-hybrid wave turbulence into the laminar model of shock surfing can explain the preferential acceleration of heavier particles as observed by Voyager at the termination shock. At relativistic energies, unlimited acceleration of ions is theoretically possible; because for sufficiently strong shocks main limitation of the mechanism, caused by the escape of accelerated particles downstream of the shock during acceleration no longer exists.
|
Title: |
|
Exact nonlinear dust kinetic Alfvén waves in a dust ion plasma |
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Authors: |
|
|
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Affiliation: |
|
AA(Theoretical Plasma Physics Group, Department of Physics, Quaid-i-Azam University, Islamabad 45320, Pakistan a_m_mirza@yahoo.com) |
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Journal: |
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New Journal of Physics, Volume 5, Issue 1, pp. 116 (2003). |
|
Publication Date: |
|
09/2003 |
|
Origin: |
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IOP |
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DOI: |
|
|
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Bibliographic Code: |
|
2003NJPh....5..116M |
The properties of nonlinear dust kinetic Alfvén waves in a collisionless, low (but finite)-bgr, dust ion plasma are investigated by employing the pseudo-potential approach, which is valid for arbitrary amplitude solitary waves. It is shown both analytically and numerically that a dusty plasma model can support solitary waves consisting of density humps or dips. Furthermore, the properties of these solitary waves are found to be significantly modified by the speed and obliqueness of the wave propagation. The findings of the present investigation should be useful in understanding the formation of coherent nonlinear soliton structures in space and astrophysical dusty plasmas, such as in planetary rings and cometary tails.
|
Title: |
|
A model for comet 81P/Wild 2 |
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Authors: |
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Journal: |
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Journal of Geophysical Research, Volume 108, Issue E10, pp. SRD 2-1, CiteID 8112, DOI 10.1029/2003JE002093 (JGRE Homepage) |
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Publication Date: |
|
09/2003 |
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Origin: |
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AGU |
|
AGU Keywords: |
|
Interplanetary Physics: Interplanetary dust, Interplanetary Physics: Instruments and techniques, Interplanetary Physics: General or miscellaneous |
|
Abstract Copyright: |
|
(c) 2003: American Geophysical |
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DOI: |
|
|
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Bibliographic Code: |
|
2003JGRE.108j.SRD2S |
A model is presented for the nucleus of comet 81P/Wild 2 and its activity, based on analysis of dust coma morphology, water and dust production, and nongravitational perturbations of the orbital motion. A four-apparition composite light curve is derived from ~500 magnitude estimates. There appear to be two major outgassing sources on the nucleus: one, near a rotation pole, sustains much of preperihelion activity; the other, on the opposite polar hemisphere and closer to the equatorial plane, accounts for the bulk of postperihelion activity. Both regions are active near perihelion. Their surface areas are estimated at 4.5 and 9.5 km2, respectively. With the nucleus probably 4.0 to 6.3 km across, the total outgassing area makes up 11 to nearly 30% of the nucleus surface, unusually high for a short-period comet, yet consistent with relatively small perturbations of the orbital motion, driven by the momentum transferred to the nucleus by water sublimation. The absence of a more prominent nongravitational effect may largely be due to high dust mass loading of the gas flow, implying its subsonic initial speed. Indeed, the dustier, polar source appears to be the less efficient of the two in transferring the momentum to the nucleus. The comet's short history in the innermost solar system region could account for the relatively large outgassing fraction of the surface. At the Stardust encounter time, more than three months after perihelion, only the near-equatorial source (the larger, less dusty one) is expected to be active.
|
Title: |
|
Rotation and cometary activity of KBO (29981) 1999 TD10 |
|
Authors: |
|
|
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Affiliation: |
|
AA(Department of Geophysics and Planetary Sciences, |
|
Journal: |
|
Icarus, Volume 165, Issue 1, p. 101-111. (Icarus Homepage) |
|
Publication Date: |
|
09/2003 |
|
Origin: |
|
ELSEVIER |
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Abstract Copyright: |
|
(c) 2003 Elsevier ( |
|
DOI: |
|
|
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Bibliographic Code: |
|
2003Icar..165..101C |
We describe observations of the scattered Kuiper Belt object (29981) 1999 TD10 performed during five observing runs at two observatories, over 370 days from 2000 September to 2001 September. They show significant brightness variations that fit a double-peaked lightcurve with period /15.448+/-0.012 h in /V and /R bands. The phase effect in /V band, /0.09+/-0.01 magdeg-1, is smaller than that of Pluto but larger than that of several KBOs, while in /R band it is /0.030+/-0.005 magdeg-1. We find color variation between the two bands, which implies a non-homogeneous albedo distribution on the surface. Evidence of surface activity near perihelion in the form of a coma/tail is presented using radial image profiles and a 2D contour map.
|
Title: |
|
Silicate stardust from comets |
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Authors: |
|
|
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Journal: |
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Geochimica et Cosmochimica Acta Supplement, Vol. 67, Issue 18, p.288 |
|
Publication Date: |
|
09/2003 |
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Origin: |
|
ADS |
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Bibliographic Code: |
|
2003GeCAS..67Q.288M |
Not Available
|
Title: |
|
The Anti-Tail of Comet C/1995 O1 (Hale-Bopp) in 1997/1998 |
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Authors: |
|
|
|
Affiliation: |
|
AA(European Southern Observatory, Alonso de Cordova 3107, Santiago de Chile and Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany) |
|
Journal: |
|
Earth, Moon, and Planets, v. 93, Issue 1, p. 19-35 (2003). (EM&P Homepage) |
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Publication Date: |
|
09/2003 |
|
Origin: |
|
KLUWER |
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Keywords: |
|
Comet C/1995 O1 Hale-Bopp, anti-tail, neck-line structure, mm-size dust |
|
DOI: |
|
|
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Bibliographic Code: |
|
2003EM&P...93...19B |
The large-scale post-perihelion
evolution of the dust tail in Comet C/1995 O1 (Hale-Bopp) was monitored with
Schmidt telescope exposures at the European Southern Observatory (ESO) La Silla
in
|
Title: |
|
Tidal Breakup of Comets |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Institutes of Astronomy and Space Science, National Central University, Chung-Li, Taiwan 32054, ROC, e-mail: wingip@astro.ncu.edu.tw) |
|
Journal: |
|
Celestial Mechanics and Dynamical Astronomy, v. 87, Issue 1, p. 197-202 (2003). (CeMDA Homepage) |
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Publication Date: |
|
09/2003 |
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Origin: |
|
KLUWER |
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Abstract Copyright: |
|
(c) 2003 Kluwer Academic Publishers |
|
Bibliographic Code: |
|
2003CeMDA..87..197I |
In the context of the survival of periodic comets of different origins, rotational breakup and tidal disruption could be important, especially of the short period comets injected from the Kuiper belt. This is because long-period comets from the distant Oort cloud tend to be subject to thermal stress and volatile `explosion' far more severely. A simple calculation using the Öpik method of random planetary close encounters was performed to estimate the probability of tidal disruption of comets and scattered Kuiper belt objects (SKBOs) during their orbital migration. It was found that a large fraction of the short period comets and SKBOs might have been internally fragmented by single or multiple close encounters with the outer planets.
|
Title: |
|
Irregular Particles in Comet C/1995 O1 Hale-Bopp Inferred from its Mid-Infrared Spectrum |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Instituto de
Astrofísica de Andalucía, CSIC, P.O. Box 3004, 18008 Granada, Spain; fernando@iaa.es), AB(Instituto de Astrofísica de Andalucía, CSIC,
P.O. Box 3004, 18008 Granada, Spain; fernando@iaa.es), AC(Universidad Politécnica de Valencia, Valencia,
Spain), AD(Departamento de Física Aplicada, Universidad de Granada; and
Instituto de Astrofísica de Andalucía, CSIC, P.O. Box 3004, 18008 Granada,
Spain) |
|
Journal: |
|
The Astrophysical Journal, Volume 595, Issue 1, pp. 522-530. (ApJ Homepage) |
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Publication Date: |
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09/2003 |
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Origin: |
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UCP |
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ApJ Keywords: |
|
Comets: General, Comets: Individual: Name: Hale-Bopp (C/1995 O1), ISM: Dust, Extinction, Infrared: Solar System |
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Abstract Copyright: |
|
(c) 2003: The American Astronomical Society |
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DOI: |
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Bibliographic Code: |
|
2003ApJ...595..522M |
An analysis of the Infrared Space Observatory (ISO) infrared spectra of comet C/1995 O1 Hale-Bopp has been conducted. The particles in the coma are assumed to be irregular aggregates that are built by a diffusion-limited aggregation (DLA) procedure and are composed of olivine, both amorphous and crystalline, and glassy carbon. To simulate the morphological structure of the interstellar dust, the silicate component is placed in the inner layers of the aggregate, while the carbon dipoles occupy the outermost layers. The particle emissivities are calculated using the discrete dipole approximation (DDA) method of Draine & Flatau. The dust size distribution functions at different heliocentric distances (2.8, 2.9, and 3.9 AU) have been determined as the solution to three overdetermined systems of equations for the infrared flux at each wavelength in the 8-40 μm region. These size distributions can be well fitted by a power law, n(r)~r-α, having power indexes that decrease with heliocentric distance as α=-3.6+/-0.3 at 2.8 AU and -3.3+/-0.3 at 3.9 AU.
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Title: |
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Dust production and coma morphology of 67P/Churyumov-Gerasimenko during the 2002-2003 apparition |
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Authors: |
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|
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Affiliation: |
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AA(Instituto de
Astrofísica de Canarias (IAC), C/Vía Láctea s/n, 38205 La Laguna, Tenerife,
Spain) |
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Journal: |
|
Astronomy and Astrophysics, v.408, p.767-774 (2003) (A&A Homepage) |
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Publication Date: |
|
09/2003 |
|
Origin: |
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A&A |
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A&A Keywords: |
|
comets: individual: 67P/Churyumov-Gerasimenko, techniques: photometric |
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DOI: |
|
|
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Bibliographic Code: |
|
2003A&A...408..767K |
Light curves and images of 67P/Churyumov-Gerasimenko are presented for the 2002-2003 apparition based on amateur CCD monitoring using a standardised method to produce consistent photometry in Johnson-Kron-Cousins system. Multiaperture data shows a large outburst at perihelion during which dust production increased by a factor of 2 to give a peak value of Afrho ~350 cm. A similar outburst was seen at the same epoch of the previous apparition in 1995-96 and probably in 1982-83, suggesting that the light curve is similar at succesive returns. A considerable change is seen in the slope of the light curve at r=1.85 AU (T+140 days) corresponding to a second significant increase in dust production. Overall though the dust production shows a very steep dependence with heliocentric distance, falling as r-5.8.
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Title: |
|
The evolution of comets in the Oort cloud and Kuiper belt |
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Authors: |
|
|
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Affiliation: |
|
AA(Department of Space Studies, Southwest Research
Institute, |
|
Journal: |
|
Nature, Volume 424, Issue 6949, pp. 639-642 (2003). (Nature Homepage) |
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Publication Date: |
|
08/2003 |
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Origin: |
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NATURE |
|
Bibliographic Code: |
|
2003Natur.424..639S |
Comets are remnants from the time when the outer planets formed, ~4-4.5 billion years ago. They have been in storage since then in the Oort cloud and Kuiper belt-distant regions that are so cold and sparsely populated that it was long thought that comets approaching the Sun were pristine samples from the time of Solar System formation. It is now recognized, however, that a variety of subtle but important evolutionary mechanisms operate on comets during their long storage, so they can no longer be regarded as wholly pristine.
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Title: |
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The formation of the crater structure on the surface of a cometary nucleus by meteoroid impacts |
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Authors: |
|
|
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Journal: |
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Kinematika i
Fizika Nebesnykh Tel, vol. 19, no. 4, p. 367-373 |
|
Publication Date: |
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08/2003 |
|
Origin: |
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KFNT |
|
Language: |
|
Ukrainian |
|
Bibliographic Code: |
|
2003KFNT...19..367S |
Several mechanisms of the formation of craters on the surface of a cometary nucleus are possible: the orbital evolution of an inhomogeneous nucleus, a meteoroid impact, an intensive vaporization of bulk CO2/CO inclusions, and a heat explosion due to the crystallization of amorphous ice or the recombination of hydrated ions. One of the possible mechanisms of the formation of the crater structure on the surface of a cometary nucleus, namely meteoroid impacts is considered. The probability of the simultaneous existence of several craters on the same nucleus is calculated with respect to different lifetimes and their formation frequency.
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Title: |
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CCD observations of distant comets from Palomar and Steward Observatories |
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Authors: |
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|
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Affiliation: |
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AA(Jet Propulsion Laboratory, MS 183-601, 4800 Oak Grove Drive, 91109, Pasadena, CA, USA), AB(Jet Propulsion Laboratory, MS 183-601, 4800 Oak Grove Drive, 91109, Pasadena, CA, USA) |
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Journal: |
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Icarus, Volume 164, Issue 2, p. 492-503. (Icarus Homepage) |
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Publication Date: |
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08/2003 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
|
(c) 2003 Elsevier ( |
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DOI: |
|
|
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Bibliographic Code: |
|
2003Icar..164..492L |
We are conducting a ground-based observational study of distant cometary nuclei with the aim of increasing the current database of physical parameters of individual objects, and to estimate the overall distributions of size, rotation period, axial ratio, and color indices. Additionally, we are obtaining CCD spectroscopy and photometry of established and potential targets of current and future spacecraft missions. The results presented here are derived from CCD imaging obtained using the 2.3-m Bok telescope of Steward Observatory (Arizona), obtained in May 2001, and the 5-m Hale telescope at Palomar Observatory (California), obtained in May 2000 and March 2001. Comets observed include 4P/Faye, 6P/d'Arrest, 22P/Kopff, 36P/Whipple, 50P/Arend, 78P/Gehrels 2, 92P/Sanguin, 107P/Wilson-Harrington, and 128P/Shoemaker-Holt 1-A. Of the nine comets observed, only Comets 4P/Faye and 50P/Arend displayed visible coma activity. We have performed either single /R filter or multi-filter (BVRI) measurements on these comets, from which we obtain radius and broadband color estimates as well as /Afρ values for the active comets. For selected objects we have performed time-series /R filter imaging from which we have derived the rotation period and lower limits on the nuclear axial ratio and density. The radius results obtained are included in the cometary nucleus size distribution estimate by Weissman and Lowry (2003).
|
Title: |
|
The nucleus of Deep Impact target Comet 9P/Tempel 1 |
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Authors: |
|
Fernández, Y. R.; Meech, K. J.; Lisse, C. M.; A'Hearn, M. F.; Pittichová, J.; Belton, M. J. S. |
|
Affiliation: |
|
AA(Institute for Astronomy, University of Hawai`i, 2680 Woodlawn Drive, 96822, Honolulu, HI, USA), AB(Institute for Astronomy, University of Hawai`i, 2680 Woodlawn Drive, 96822, Honolulu, HI, USA), AC(Department of Astronomy, University of Maryland, 20742-2421, College Park, MD, USA), AD(Department of Astronomy, University of Maryland, 20742-2421, College Park, MD, USA), AE(Institute for Astronomy, University of Hawai`i, 2680 Woodlawn Drive, 96822, Honolulu, HI, USA), AF(Belton Space Exploration Initiatives, 430 S. Randolph Way, 85716, Tucson, AZ, USA) |
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Journal: |
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Icarus, Volume 164, Issue 2, p. 481-491. (Icarus Homepage) |
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Publication Date: |
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08/2003 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
|
(c) 2003 Elsevier ( |
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DOI: |
|
|
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Bibliographic Code: |
|
2003Icar..164..481F |
On UT 2000 August 21 we obtained simultaneous visible and mid-infrared observations of Comet 9P/Tempel 1, the target of the upcoming NASA Discovery Program mission Deep Impact. The comet was still quite active while 2.55 AU from the Sun (post-perihelion). Two independent analyses of our data, one parameterizing the coma morphology and the other modeling infrared spectrophotometry, show that the nucleus's cross section at the time the data were taken corresponds to an effective radius of /3.0+/-0.2 km. Based on visible-wavelength photometry of the comet taken during this observing run and others in the summer of 2000, all of which show the rotational modulation of the nucleus's brightness, we find that the infrared data were obtained near the maximum of the light curve. If we assume that the nucleus's light curve had a peak-to-valley range of /0.6+/-0.2 mag, then the mean effective radius is /2.6+/-0.2 km. Visible-wavelength photometry of the nucleus, including data published by other groups, lets us constrain the nucleus's R-band geometric albedo: /0.072+/-0.016. The nucleus's flux contributed about 85% of the light in the mid-infrared images.
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Title: |
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New spin period determination for comet 6P/d'Arrest |
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Authors: |
|
Gutiérrez, P. J.; de León, J.; Jorda, L.; Licandro, J.; Lara, L. M.; Lamy, P. |
|
Affiliation: |
|
AA(Laboratoire
d'Astrophysique de Marseille, BP 8, 13376 Marseille Cedex 12, France),
AB(Instituto de Astrofísica de Canarias, C/Via Lactea s/n, 38200 La Laguna,
Tenerife, Spain), AC(Laboratoire d'Astrophysique de Marseille, BP 8, 13376
Marseille Cedex 12, France), AD(Isaac Newton Group of Telescopes & Instituto
de Astrofísica de Canarias, PO Box 321, 38700 Santa Cruz de La Palma,
Tenerife, Spain), AE(Instituto de Astrofísica de Andalucía, CSIC, PO Box
3004, 18080 Granada, Spain), AF(Laboratoire d'Astrophysique de Marseille, BP
8, 13376 Marseille Cedex 12, France) |
|
Journal: |
|
Astronomy and Astrophysics, v.407, p.L37-L40 (2003) (A&A Homepage) |
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Publication Date: |
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08/2003 |
|
Origin: |
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A&A |
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A&A Keywords: |
|
comets: individual: 6P/d'Arrest |
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DOI: |
|
|
|
Bibliographic Code: |
|
2003A&A...407L..37G |
A lightcurve of comet 6P/d'Arrest
from R-band CCD images taken at
|
Title: |
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Optical properties of cometary dust. Constraints from numerical studies on light scattering by aggregate particles |
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Authors: |
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|
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Affiliation: |
|
AA(Institut für Planetologie, Westfälische Wilhelms-Universität, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany), AB(Department of Astronomy, 211 SSRB, University of Florida, Gainesville, FL 32611-2055, USA), AC(Institut für Planetologie, Westfälische Wilhelms-Universität, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany) |
|
Journal: |
|
Astronomy and Astrophysics, v.407, p.L5-L8 (2003) (A&A Homepage) |
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Publication Date: |
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08/2003 |
|
Origin: |
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A&A |
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A&A Keywords: |
|
comets: general, interplanetary medium, meteors, meteoroids, polarization, scattering |
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DOI: |
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|
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Bibliographic Code: |
|
2003A&A...407L...5K |
Optical observations of cometary dust have revealed that the solar radiation scattered by the dust has common characteristics in the phase-angle and wavelength dependences of intensity (including albedo) and polarization, irrespective of the properties of the parent comets. We present numerical calculations on light scattering by clusters of spheres showing that all of these common optical properties are reproduced by large aggregates consisting of optically dark submicron grains. Our model neither invokes any averaging of the results over size and/or composition of the aggregates nor needs to specify the configuration of the constituent grains. The refractive indices used in this model are consistent with a mixture of silicates, metals, and carbonaceous compounds with the element abundances of cometary dust.
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Title: |
|
Long-term simulations of the rotational state of small irregular cometary nuclei |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Laboratoire
d'Astrophysique de Marseille, BP 8, 13376 Marseille Cedex 12, France),
AB(Laboratoire d'Astrophysique de Marseille, BP 8, 13376 Marseille Cedex 12,
France), AC(Instituto de Astrofísica de Andalucía, CSIC, PO Box 3004, 18080
Granada, Spain), AD(Instituto de Astrofísica de Andalucía, CSIC, PO Box 3004,
18080 Granada, Spain) |
|
Journal: |
|
Astronomy and Astrophysics, v.406, p.1123-1133 (2003) (A&A Homepage) |
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Publication Date: |
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08/2003 |
|
Origin: |
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A&A |
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A&A Keywords: |
|
comets: general |
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DOI: |
|
|
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Bibliographic Code: |
|
2003A&A...406.1123G |
We have performed simulations of the long-term evolution of the spin state of small active comet nuclei (1 km and 0.6 km) in the orbit of 46P/Wirtanen under the effect of the torque of the nongravitational force. A total of 46 combinations of irregular shapes and activity patterns have been simulated. We observe typical changes of the spin period of 0.01-10 h at each perihelion passage during the simulations, depending on the initial spin period and on the temporal evolution of the spin state. The direction of the angular momentum also changes by 0.1 to several tens of degrees per orbit. These changes are not always associated with an observable excitation of the spin state. While the nucleus gets to excited spin states in some simulations, it remains in a pure spin state during several tens of orbits in others. Therefore, even small and very active nuclei like 46P/Wirtanen could remain in their spin state of minimum energy (pure spin) during at least several tens of perihelion passages. We find that, for the parameters used in our simulation, a drastic increase in spin period to ~ 200 h is required before the excitation of the spin state can occur. Further results and their consequences for the observations of rotational parameters of cometary nuclei are thoroughly described in the text.
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Title: |
|
Sintering of highly porous silica-particle samples: analogues of early Solar-System aggregates |
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Authors: |
|
|
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Affiliation: |
|
AA(Astrophysikalisches Institut und
Universitäts-Sternwarte, Schillergäßchen 2, 07745, |
|
Journal: |
|
Icarus, Volume 164, Issue 1, p. 139-148. (Icarus Homepage) |
|
Publication Date: |
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07/2003 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
|
(c) 2003 Elsevier ( |
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DOI: |
|
|
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Bibliographic Code: |
|
2003Icar..164..139P |
I describe a new method to make particle layers which consist of SiO2 spheres with 0.78 μm radius. The layers were produced by sedimentation of aggregates which had grown in ballistic particle collisions, and the layers had a porosity of 0.95. They were used for experiments on sintering, i.e., the samples were heated in an oven at varying temperatures and heating durations, and the samples were analyzed by scanning electron microscopy. Based on the change of particle diameter, surface diffusion sintering and viscous flow are identified as important transformation mechanisms. The first effect dominated at the start of restructuring and the latter at higher temperatures. The neck growth of adjacent particles was fitted to a surface diffusion sintering model and predicts neck radii as a heating temperature and duration function. Between the temperature range of neck formation and of melting, further restructuring occurred which lead to dissolution of particulate structure and to densification and which resulted in a porous object consisting of straight elongated substructures which connected kinks of higher material density. The thermal transformation is important for the change of strength, collisional behavior, light-scattering properties, and thermal conductivity with relevance to dust aggregates, planetesimals, comets, interplanetary dust particles, and regolith-covered celestial bodies.
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Title: |
|
The Influence of Reactive Torques on Comet Nucleus Rotation |
|
Authors: |
|
Neishtadt, A. I.; Scheeres, D. J.; Sidorenko, V. V.; Stooke, P. J.; Vasiliev, A. A. |
|
Affiliation: |
|
AA(Space Research Institute, Moscow, Russia), AB(Department of Aerospace Engineering, The University of Michigan, Ann Arbor, MI, U.S.A.), AC(Keldysh Institute of Applied Mathematics, Miusskaya Sq. 4, 125047, Moscow, Russia), AD(Author for correspondence: Tel.: +7-0952507876 Fax: +7-0959720737 e-mail: sidorenk@spp.keldysh.ru), AE(Department of Geography, The University of Western Ontario, London, Ont, Canada) |
|
Journal: |
|
Celestial Mechanics and Dynamical Astronomy, v. 86, Issue 3, p. 249-275 (2003). (CeMDA Homepage) |
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Publication Date: |
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07/2003 |
|
Origin: |
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KLUWER |
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Abstract Copyright: |
|
(c) 2003 Kluwer Academic Publishers |
|
Bibliographic Code: |
|
2003CeMDA..86..249N |
Reactive torques, due to anisotropic sublimation on a comet nucleus surface, produce slow variations of its rotation. In this paper the secular effects of this sublimation are studied. The general rotational equations of motion are averaged over unperturbed fast rotation around the mass center (Euler-Poinsot motion) and over the orbital comet motion. We discuss the parameters that define typical properties of the rotational evolution and discover different classifications of the rotational evolution. As an example we discuss some possible scenarios of rotational evolution for the nuclei of the comets Halley and Borrelly.
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Title: |
|
Peculiar Pair of Distant Periodic Comets C/2002 A1 and C/2002 A2 (LINEAR) |
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Authors: |
|
Sekanina, Zdenek; Chodas, Paul W.; Tichý, Miloš; Tichá, Jana; Kočer, Michal |
|
Affiliation: |
|
AA(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109; zs@sek.jpl.nasa.gov, ), AB(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109; zs@sek.jpl.nasa.gov, ), AC(Kleť Observatory, Zátkovo nábřeží 4, CZ-370 01 České Budějovice, Czech Republic; mtichy@klet.cz, jticha@klet.cz, kocer@klet.cz), AD(Kleť Observatory, Zátkovo nábřeží 4, CZ-370 01 České Budějovice, Czech Republic; mtichy@klet.cz, jticha@klet.cz, kocer@klet.cz), AE(Kleť Observatory, Zátkovo nábřeží 4, CZ-370 01 České Budějovice, Czech Republic; mtichy@klet.cz, jticha@klet.cz, kocer@klet.cz) |
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Journal: |
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The Astrophysical Journal, Volume 591, Issue 1, pp. L67-L70. (ApJ Homepage) |
|
Publication Date: |
|
07/2003 |
|
Origin: |
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UCP |
|
ApJ Keywords: |
|
Comets: General, Comets: Individual: Alphanumeric: C/2002 A1, Comets: Individual: Alphanumeric: C/2002 A2, Methods: Data Analysis |
|
Abstract Copyright: |
|
(c) 2003: The American Astronomical Society |
|
DOI: |
|
|
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Bibliographic Code: |
|
2003ApJ...591L..67S |
Distant comets C/2002 A1 and C/2002 A2 make up a peculiar pair that moves about the Sun in virtually identical, somewhat unstable orbits, extending currently between about 4.7 and 29 AU from the Sun. The two objects, observed since late 2001, are unquestionably of common origin. Analysis of their relative motion indicates that their parent body split nontidally most probably between mid-1977 and early 1979 at a heliocentric distance of 22.5+/-0.1 AU and about 2.5 AU below the ecliptic, with a separation velocity of 2.7+/-0.2 m s-1. The motion of C/2002 A2, the secondary component that trails behind the primary, is found to be affected by a nongravitational deceleration of (13.4+/-1.5)×10-5 units of solar gravitational acceleration relative to C/2002 A1, which is in a range of decelerations that companions of split comets are usually subjected to. C/2002 A2 was somewhat less condensed and, interestingly, brighter than C/2002 A1.
|
Title: |
|
Hubble Space Telescope STIS Observations of Comet 19P/Borrelly during the Deep Space 1 Encounter |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723-6099 .), AB(Department of Space Studies, Southwest Research Institute, 1050 Walnut Street, Suite 426, Boulder, CO 80302; astern@swri.edu, joel@boulder.swri.edu.), AC(Department of Space Studies, Southwest Research Institute, 1050 Walnut Street, Suite 426, Boulder, CO 80302; astern@swri.edu, joel@boulder.swri.edu.) |
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Journal: |
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The Astronomical Journal, Volume 126, Issue 1, pp. 444-451. (AJ Homepage) |
|
Publication Date: |
|
07/2003 |
|
Origin: |
|
UCP |
|
AJ Keywords: |
|
Comets: General, comets: individual (19P/Borrelly), Solar System: General, Ultraviolet Emission |
|
Abstract Copyright: |
|
(c) 2003: The American Astronomical Society |
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DOI: |
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Bibliographic Code: |
|
2003AJ....126..444W |
In support of the NASA Deep Space 1 (DS1) mission to comet 19P/Borrelly, we obtained Hubble Space Telescope (HST) images and ultraviolet (UV) spectra of the comet near the time of the DS1 flyby in 2001 September. The HST data provide context information on 19P/Borrelly's circumnuclear dust environment, the rotational period and rotational phase of its nucleus, the H2O and CS2 production rates, the dust production rate, the dust reflectivity in the visible and mid-UV, and the time variability of these quantities around the time of the DS1 encounter. We derive average values of QH2O=(3.0+/-0.6)×1028 molecules s-1, [CS2/H2O]=(1.0+/-0.3)×10-3, and Qdust~240 kg s-1. The corresponding dust-to-gas mass ratio is 0.24, but this is only a rough estimate because the dust production rate is uncertain by about an order of magnitude. The dust continuum was strongly reddened between 2400 and 3200 Å, and the Afρ value of 745+/-15 cm near 6500 Å was ~2.5 times larger than the value near 2900 Å. The observed coma morphology consisted of a strong jet centered ~6° from the projected solar vector, one broad fan centered ~23° from the sunward direction, and another broad fan centered ~18° from the antisunward direction. The light curve of the optical continuum, as measured in target acquisition images, has an amplitude of ~40% in a square aperture that subtends 160 km at the comet; the rotational period could not be independently derived from the HST images but is consistent with the value of ~26 hr derived from HST observations in 1994 and ground-based images in 2000. The new HST data reveal a prominent offset in the emission peak of neutral gas molecules, and therefore in the peak column densities of gas in the coma, relative to the position of the cometary nucleus, which may be related to the offset in ion densities observed in situ by the DS1 Plasma Experiment for Planetary Exploration (PEPE) plasma spectrometer.
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Title: |
|
Polarization studies of comet C/2000 WM1 (LINEAR) |
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Authors: |
|
|
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Affiliation: |
|
AA(Physical Research Laboratory, Ahmedabad 380009, |
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Journal: |
|
Astronomy and Astrophysics, v.405, p.1129-1135 (2003) (A&A Homepage) |
|
Publication Date: |
|
07/2003 |
|
Origin: |
|
A&A |
|
A&A Keywords: |
|
comets: individual: C/2000 WM1 (LINEAR) |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2003A&A...405.1129J |
Linear polarization observations were carried out on comet C/2000 WM1 with the 1.2 m telescope at Mt. Abu Observatory during November 2001 and March 2002. The observations in November were at low phase angle (<22degr ) when the polarization is negative and where the data for most of the comets are rather meager. The observations during March were made when the phase angle was ~ 47 degr. Observations were conducted through the IHW narrow band and BVR broad band filters. Based on these polarization observations we infer that the comet C/2000 WM1 belongs to high polarization class i.e. the dusty comet family.
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Title: |
|
Laboratory Simulation of Charge Exchange-Produced X-ray Emission from Comets |
|
Authors: |
|
Beiersdorfer, P.; Boyce, K. R.; Brown, G. V.; Chen, H.; Kahn, S. M.; Kelley, R. L.; May, M.; Olson, R. E.; Porter, F. S.; Stahle, C. K.; Tillotson, W. A. |
|
Affiliation: |
|
AA(Lawrence Livermore National Laboratory, 7000 East Avenue, L-260, Livermore, CA 94550, USA.), AB(NASA/Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA.), AC(NASA/Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA.), AD(Lawrence Livermore National Laboratory, 7000 East Avenue, L-260, Livermore, CA 94550, USA.), AE(Department of Physics, Columbia University, 538 West 120th Street, New York, NY 10027, USA.), AF(NASA/Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA.), AG(Lawrence Livermore National Laboratory, 7000 East Avenue, L-260, Livermore, CA 94550, USA.), AH(University of Missouri-Rolla, Department of Physics, 1870 Miner Circle, Rolla, MO 65409, USA.), AI(NASA/Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA.), AJ(NASA/Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA.), AK(NASA/Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA.) |
|
Journal: |
|
Science, Volume 300, Issue 5625, pp. 1558-1560 (2003). |
|
Publication Date: |
|
06/2003 |
|
Category: |
|
PLANET SCI |
|
Origin: |
|
SCIENCE |
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Abstract Copyright: |
|
(c) 2003: Science |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2003Sci...300.1558B |
In laboratory experiments using the engineering spare microcalorimeter detector from the ASTRO-E satellite mission, we recorded the x-ray emission of highly charged ions of carbon, nitrogen, and oxygen, which simulates charge exchange reactions between heavy ions in the solar wind and neutral gases in cometary comae. The spectra are complex and do not readily match predictions. We developed a charge exchange emission model that successfully reproduces the soft x-ray spectrum of comet Linear C/1999 S4, observed with the Chandra X-ray Observatory.
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Title: |
|
Physics and chemistry of icy particles in the universe: answers from microgravity |
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Authors: |
|
Ehrenfreund, P.; Fraser, H. J.; Blum, J.; Cartwright, J. H. E.; García-Ruiz, J. M.; Hadamcik, E.; Levasseur-Regourd, A. C.; Price, S.; Prodi, F.; Sarkissian, A. |
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Affiliation: |
|
AA(Leiden Observatory, P.O. Box 9513, NL-2300, RA Leiden, The Netherlands), AB(Raymond & Beverly Sackler Laboratory for Astrophysics, Leiden Observatory, P.O. Box 9513, NL-2300, RA Leiden, The Netherlands), AC(Astrophysikalisches Institut und Universitaets-Sternwarte, Schillergaesschen 2, D-07745, Jena, Germany), AD(Instituto Andaluz de Ciencias de la Tierra, Laboratorio de Estudios Cristalográficos, Facultad de Ciencias, Av. Fuentenueva s/n, E-18002, Granada, Spain), AE(Instituto Andaluz de Ciencias de la Tierra, Laboratorio de Estudios Cristalográficos, Facultad de Ciencias, Av. Fuentenueva s/n, E-18002, Granada, Spain), AF(Service d'Aéronomie/CNRS, Route de Gatines, BP 3, F-91371, Verrières le Buisson, France), AG(Service d'Aéronomie/CNRS, Route de Gatines, BP 3, F-91371, Verrières le Buisson, France), AH(Department of Chemistry, University College London, 20 Gordon Street, WC1H 0AJ, London, UK), AI(Institute of Atmospheric and Ocean Sciences, Via P. Gobetti, 101, C.A.P. I-40129, Bologna, Italy), AJ(Service d'Aéronomie/CNRS, Route de Gatines, BP 3, F-91371, Verrières le Buisson, France) |
|
Journal: |
|
Planetary and Space Science, Volume 51, Issue 7-8, p. 473-494. (P&SS Homepage) |
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Publication Date: |
|
06/2003 |
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Origin: |
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ELSEVIER |
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Bibliographic Code: |
|
2003P&SS...51..473E |
During the last century, the presence of icy particles throughout the universe has been confirmed by numerous ground and space based observations. Ultrathin icy layers are known to cover dust particles within the cold regions of the interstellar medium, and drive a rich chemistry in energetic star-forming regions. The polar caps of terrestrial planets, as well as most of the outer-solar-system satellites, are covered with an icy surface. Smaller solar system bodies, such as comets and Kuiper Belt Objects (KBOs), contain a significant fraction of icy materials. Icy particles are also present in planetary atmospheres and play an important role in determining the climate and the environmental conditions on our host planet, Earth. Water ice seems universal in space and is by far the most abundant condensed-phase species in our universe. Many research groups have focused their efforts on understanding the physical and chemical nature of water ice. However, open questions remain as to whether ices produced in Earth's laboratories are indeed good analogs for ices observed in space environments. Although temperature and pressure conditions can be very well controlled in the laboratory, it is very difficult to simulate the time-scales and gravity conditions of space environments. The bulk structure of ice, and the catalytic properties of the surface, could be rather different when formed in zero gravity in space.
The author list comprises the members of the ESA Topical Team: Physico-chemistry of ices in space. In this paper we present recent results including ground-based experiments on ice and dust, models as well as related space experiments performed under microgravity conditions. We also investigate the possibilities of designing a new infrastructure, and /or making improvements to the existing hardware in order to study ices on the International Space Station (ISS). The type of multidisciplinary facility that we describe will support research in crystal growth of ices and other solid refractory materials, aerosol microphysics, light scattering properties of solid particles, the physics of icy particle aggregates, and radiation processing of molecular ices. Studying ices in microgravity conditions will provide us with fundamental data on the nature of extraterrestrial ices and allow us to enhance our knowledge on the physical and chemical processes prevailing in different space environments.
|
Title: |
|
Interiors of small bodies: foundations and perspectives |
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Authors: |
|
Binzel, Richard P.; A'Hearn, Michael; Asphaug, Erik; Barucci, M. Antonella; Belton, Michael; Benz, Willy; Cellino, Alberto; Festou, Michel C.; Fulchignoni, Marcello; Harris, Alan W.; Rossi, Alessandro; Zuber, Maria T. |
|
Affiliation: |
|
AA(Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 01239, Cambridge, MA, USA), AB(Astronomy Program, University of Maryland, 20742, College Park, MD, USA), AC(Earth Sciences Department, University of California, 95064, Santa Cruz, CA, USA), AD(LESIA, Observatoire de Paris a Meudon, 92195 , Cedex, Meudon, France), AE(Belton Space Exploration Initiatives, 85716, Tucson, AZ, USA), AF(Physikalisches Institut, University of Bern,, Bern, Switzerland), AG(INAF-Osservatorio Astronomico di Torino, 10025, Pino Torinese, Italy), AH(Observatoire Midi-Pyrénées,, Toulouse, France), AI(LESIA, Observatoire de Paris a Meudon, 92195 , Cedex, Meudon, France), AJ(Space Science Institute, 4603 Orange Knoll, 91011, La Canada, CA, USA), AK(ISTI-CNR, CNR - Area della Ricerca di Pisa, Via Moruzzi 1, 56124, Pisa, Italy), AL(Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 01239, Cambridge, MA, USA) |
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Journal: |
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Planetary and Space Science, Volume 51, Issue 7-8, p. 443-454. (P&SS Homepage) |
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Publication Date: |
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06/2003 |
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Origin: |
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ELSEVIER |
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Bibliographic Code: |
|
2003P&SS...51..443B |
With the surface properties and shapes of solar system small bodies (comets and asteroids) now being routinely revealed by spacecraft and Earth-based radar, understanding their interior structure represents the next frontier in our exploration of these worlds. Principal unknowns include the complex interactions between material strength and gravity in environments that are dominated by collisions and thermal processes. Our purpose for this review is to use our current knowledge of small body interiors as a foundation to define the science questions which motivate their continued study: In which bodies do ``planetary'' processes occur? Which bodies are ``accretion survivors'', i.e., bodies whose current form and internal structure are not substantially altered from the time of formation? At what characteristic sizes are we most likely to find ``rubble-piles'', i.e., substantially fractured (but not reorganized) interiors, and intact monolith-like bodies? From afar, precise determinations of newly discovered satellite orbits provide the best prospect for yielding masses from which densities may be inferred for a diverse range of near-Earth, main-belt, Trojan, and Kuiper belt objects. Through digital modeling of collision outcomes, bodies that are the most thoroughly fractured (and weak in the sense of having almost zero tensile strength) may be the strongest in the sense of being able to survive against disruptive collisions. Thoroughly fractured bodies may be found at almost any size, and because of their apparent resistance to disruptive collisions, may be the most commonly found interior state for small bodies in the solar system today. Advances in the precise tracking of spacecraft are giving promise to high-order measurements of the gravity fields determined by rendezvous missions. Solving these gravity fields for uniquely revealing internal structure requires active experiments, a major new direction for technological advancement in the coming decade. We note the motivation for understanding the interior properties of small bodies is both scientific and pragmatic, as such knowledge is also essential for considering impact mitigation.
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Title: |
|
Evidence for a dominant native source of carbon monoxide in Comet C/1996 B2 (Hyakutake) |
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Authors: |
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DiSanti, Michael A.; Mumma, Michael J.; Dello Russo, Neil; Magee-Sauer, Karen; Griep, David M. |
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Journal: |
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Journal of Geophysical Research Planets, Volume 108, Issue E6, pp. 15-1, CiteID 5061, DOI 10.1029/2002JE001961 (JGRE Homepage) |
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Publication Date: |
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06/2003 |
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Origin: |
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AGU |
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AGU Keywords: |
|
Planetology: Comets and Small Bodies: Atmospheres-composition and chemistry, Planetology: Solar System Objects: Comets, Planetology: Comets and Small Bodies: Composition, Planetology: Comets and Small Bodies: Radiation and spectra, Planetology: Comets and Small Bodies: Remote sensing |
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Abstract Copyright: |
|
(c) 2003: American Geophysical |
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DOI: |
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Bibliographic Code: |
|
2003JGRE.108f...15D |
Carbon monoxide was measured in C/1996 B2 (Hyakutake) on four preperihelion dates, UT 1996 March 24.5 and April 10.2-12.2, using CSHELL at the NASA Infrared Telescope Facility on Mauna Kea, Hawaii. These observations provided the first secure ground-based detection of cometary CO at infrared wavelengths. The rotational temperatures retrieved for CO are consistent with a heliocentric dependence Trot = 63 Rh -1.06 K over the range Rh = 1.06-0.64 AU. From long-slit analysis we distinguish native and distributed sources of CO, and we infer the relative abundance of native to total CO to be 0.773 +/- 0.054 on April 12.2. If this ratio is constant on UT April 11.2 and 12.2, the mean mixing ratios (relative to water) are 0.149 +/- 0.019 for native CO and 0.191 +/- 0.022 for the sum of native and extended sources. These mixing ratios are based on direct measurements of H2O made on the same dates with the same instrument and analyzed with the same data processing algorithms. The observed spatial scale for complete development of the extended source on UT 1996 April 12.2 was consistent with that observed for C/1995 O1 (Hale-Bopp) on UT 1997 January 21, after taking into account differences in outflow velocity and heliocentric distance assuming insolation-limited release. This may suggest similar progenitor material in these two comets.
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Title: |
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Impacts into porous foam targets: possible implications for the disruption of comet nuclei |
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Authors: |
|
|
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Affiliation: |
|
AA(Southwest Research Institute, 1050 Walnut Street Suite 400, 80302, Boulder, CO, USA), AB(Department of Physics, State University of New York Plattsburgh, 12901, Plattsburgh, NY, USA), AC(Department of Physics, State University of New York Plattsburgh, 12901, Plattsburgh, NY, USA) |
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Journal: |
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Icarus, Volume 163, Issue 2, p. 504-507. (Icarus Homepage) |
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Publication Date: |
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06/2003 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
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(c) 2003 Elsevier ( |
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DOI: |
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Bibliographic Code: |
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2003Icar..163..504D |
We have conducted a series of impact experiments to examine the response of very porous foam targets to various impacts. Under near-vacuum conditions, closed-pore and open-pore foam targets were subjected to ~1 km s-1 impacts from aluminum and foam projectiles. We found that open-pore targets absorbed the impacts with little or no global fragmentation or noticeable cratering, exhibiting only local damage along the path of the projectile, which tunneled through the target. Closed-pore targets exhibited nearly explosive disruption, apparently resulting from stresses built up within the target due to internal pressurization from air that could not escape the target interior during evacuation of the impact chamber. These results suggest that build-up of internal volatile pressure within the nuclei of collisionally or dynamically unevolved comets could allow comparatively small impacts onto their surfaces to result in disproportionately disruptive outcomes.
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Title: |
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Navier-Stokes and direct |
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Authors: |
|
Crifo, J. F.; Loukianov, G. A.; Rodionov, A. V.; Zakharov, V. V. |
|
Affiliation: |
|
AA(CNRS, Service d'Aéronomie, BP 3, F 91371, Verrières Cedex, France), AB(Center for Advanced Studies, St.-Petersburg State Technical University, Polytechnicheskaya Street, 29, 195251, St.-Petersburg, Russia), AC(Central Research Institute on Machine Building (TsNIIMASH), Pionyerskaya Street, 4, 141070, Korolev, Moscow Region, Russia), AD(Center for Advanced Studies, St.-Petersburg State Technical University, Polytechnicheskaya Street, 29, 195251, St.-Petersburg, Russia) |
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Journal: |
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Icarus, Volume 163, Issue 2, p. 479-503. (Icarus Homepage) |
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Publication Date: |
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06/2003 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
|
(c) 2003 Elsevier ( |
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DOI: |
|
|
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Bibliographic Code: |
|
2003Icar..163..479C |
The dayside near-nucleus comae
formed by solar-driven sublimation from two different aspherical nuclei made of
an homogeneous mixture of ice and dust are computed by (1) solving
Navier-Stokes equations and (2) direct
|
Title: |
|
Saturated Hydrocarbons in Comet 153P/Ikeya-Zhang: Ethane, Methane, and Monodeuterio-Methane |
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Authors: |
|
Kawakita, Hideyo; Watanabe, Jun-ichi; Kinoshita, Daisuke; Ishiguro, Masateru; Nakamura, Ryosuke |
|
Affiliation: |
|
AA(Gunma Astronomical Observatory, 6860-86 Nakayama, Takayama, Gunma 377-0702, Japan; kawakita@astron.pref.gunma.jp), AB(National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan), AC(Department of Astronomical Science, Graduate University for Advanced Studies, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan), AD(Planetary Science Division, The Institute of Space and Astronautical Science (ISAS), 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan), AE(Lunar Mission Research Center, National Space Development Agency of Japan, 2-1-1 Sengen, Tsukuba 305-8505, Japan) |
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Journal: |
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The Astrophysical Journal, Volume 590, Issue 1, pp. 573-578. (ApJ Homepage) |
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Publication Date: |
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06/2003 |
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Origin: |
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UCP |
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ApJ Keywords: |
|
Comets: General, Comets: Individual: 153P/Ikeya-Zhang, Infrared: Solar System, Molecular Data |
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Abstract Copyright: |
|
(c) 2003: The American Astronomical Society |
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DOI: |
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Bibliographic Code: |
|
2003ApJ...590..573K |
Emissions of the methane ν3 band and the ethane ν7 band were detected in the high-dispersion infrared spectra of comet 153P/Ikeya-Zhang taken by the Subaru Telescope with the Infrared Camera and Spectrograph (IRCS) on 2002 May 28 and 29 UT. The rotational temperature is estimated to be about 40-50 K from R0 and R1 lines of the methane ν3 band. The production rates of methane and ethane were estimated by applying the rotational temperature of 50 K. Resultant production rates of methane and ethane are (2.13+/-0.40)×1026 and (1.75+/-0.48)×1026 molecules s-1, respectively. The abundance ratio between ethane and methane is 0.82+/-0.27, which is comparable with other comets within error bars. Although the emissions of monodeuterio-methane (CH3D) were searched for carefully, there is no evidence of them. The 2 σ (95% confidence) upper limit of the CH3D/CH4 ratio is 0.3 in comet 153P/Ikeya-Zhang. Comparing the relative abundance of methane and ethane in the interstellar ices, we discussed the formation conditions of cometary nuclei.
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Title: |
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143P/Kowal-Mrkos and the Shapes of Cometary Nuclei |
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Authors: |
|
|
|
Affiliation: |
|
AA(Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822-1897 jewitt@ifa.hawaii.edu,sheppard@ifa.hawaii.edu, yan@ifa.hawaii.edu), AB(Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822-1897 jewitt@ifa.hawaii.edu,sheppard@ifa.hawaii.edu, yan@ifa.hawaii.edu), AC(Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822-1897 jewitt@ifa.hawaii.edu,sheppard@ifa.hawaii.edu, yan@ifa.hawaii.edu) |
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Journal: |
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The Astronomical Journal, Volume 125, Issue 6, pp. 3366-3377. (AJ Homepage) |
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Publication Date: |
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06/2003 |
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Origin: |
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UCP |
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AJ Keywords: |
|
Comets: General, Comets: Individual: Name: C/1998 K5 (143P/Kowal-Mrkos), Kuiper Belt |
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Abstract Copyright: |
|
(c) 2003: The American Astronomical Society |
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DOI: |
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Bibliographic Code: |
|
2003AJ....125.3366J |
We add 143P/Kowal-Mrkos to the small but growing sample of well-observed cometary nuclei. Photometric observations from 3.4 to 4.0 AU heliocentric distance reveal a pointlike object with no detectable outgassing. Periodic modulation of the scattered light (ΔmR=0.45+/-0.05) is attributed to rotation of the bare nucleus with a double-peaked period 17.21+/-0.10 hr and a projected ratio of the shortest to longest axis of about 0.67/1. We also measured the phase coefficient (0.043+/-0.014 mag deg-1), the BVRI colors (V-R=0.58+/-0.02), and the absolute red magnitude [mR(1, 1, 0)=13.49+/-0.20]. The effective circular radius is 5.7+/-0.6 km (geometric albedo 0.04 assumed). We study the properties of 11 well-observed Jupiter-family comet (JFC) nuclei. On average, the nuclei are systematically more elongated (average photometric range ΔmR=0.54+/-0.07) than main-belt asteroids of comparable size (ΔmR=0.32+/-0.05) and more elongated than fragments produced in laboratory impact experiments. We attribute the elongation of the nuclei to an evolutionary effect, most likely driven by sublimation-induced mass loss. However, we find no evidence for any relation between the nucleus shape and the sublimation timescale. This may be because the timescale for evolution of the nucleus shape is very short compared with the dynamical timescale for the JFCs, meaning that most nuclei in our sample are already highly physically evolved.
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Title: |
|
Cosmic dust physical properties and theICAPS facility on board the ISS |
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Authors: |
|
|
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Affiliation: |
|
AA(Université
Paris VI/Aéronomie CNRS-IPSL, BP 3, 91371 Verrières, France; aclr@aerov.jussieu.fr) |
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Journal: |
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Advances in Space Research, Volume 31, Issue 12, p. 2599-2606. (AdSpR Homepage) |
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Publication Date: |
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06/2003 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
|
(c) 2003 Elsevier Science B.V. All rights reserved. |
|
DOI: |
|
|
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Bibliographic Code: |
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2003AdSpR..31.2599L |
Cometary comae, cometary tails, and the interplanetary dust cloud, are low density dust clouds built of cosmic dust particles. Light scattering observations, from in-situ space probes and remote observatories, are a key to their physical properties. This presentation updates results on cometary and interplanetary dust derived from such observations (with emphasis on polarization), and compares them with results on asteroidal regoliths. The polarization phase curves follow similar trends, with parameters that may vary from one object to another. The wavelength dependence is highly variable, although it is usually linear in the visible domain. It may be suggested (from observations, modeling and laboratory measurements) that these dust particles are irregular, with a size greater than the wavelength, and that cometary dust is highly porous, as compared to asteroidal or interplanetary dust. Sophisticated numerical models and laboratory measurements on dust analogues are indeed required to interpret without any ambiguity the ensemble of results. The opportunity offered by the ICAPS facility (an ESA project selected for the ISS, now in phase B) to deduce the physical properties of cosmic dust particles from their optical properties, as well as their evolution (breaking-off and agglomeration, ices condensation and evaporation), is presented.
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Title: |
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Comparative study of the dust emission of 19P/Borrelly (Deep space 1) and 1P/Halley |
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Authors: |
|
Ho, T. M.; Thomas, N.; Boice, D. C.; Kollein, C.; Soderblom, L. A. |
|
Affiliation: |
|
AA(MPI fuer Aeronomie, Max-Planck-Strasse 2, 87191 Katlenburg-Lindau, Germany; hotrami@linmpi.mpg.de), AB(Physikalisches Institut, Universitaet Bern, Sidlerstrasse 5, CH-8012 Bern, Switzerland), AC(SWR1, 6220 Culebra Road, San Antonio, Texas 78228-0510, United States), AD(MPI fuer Aeronomie, Max-Planck-Strasse 2, 87191 Katlenburg-Lindau, Germany), AE(USGS, Flagsta , 2255 N Gemini Drive, Flagstaf, Arizona 86001, United States) |
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Journal: |
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Advances in Space Research, Volume 31, Issue 12, p. 2583-2589. (AdSpR Homepage) |
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Publication Date: |
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06/2003 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
|
(c) 2003 Elsevier Science B.V. All rights reserved. |
|
DOI: |
|
|
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Bibliographic Code: |
|
2003AdSpR..31.2583H |
Images obtained by the Miniature Integrated Camera and Imaging Spectrometer (MICAS) experiment onboard the Deep Space 1 spacecraft which encountered comet 19P/Borrelly on September 22nd 2001 show a dust coma dominated by jets. In particular a major collimated dust jet on the sunward side of the nucleus was observed. Our approach to analyse these features is to integrate the observed intensity in concentric envelopes around the nucleus. The same procedures has been used on the Halley Multicolour Camera images of comet 1P/Halley acquired on March 14th 1986. We are able to show that at Borrelly the dust brightness dependence as a function of radial distance is different to that of Halley. At large distances both comets show constant values as the size of the concentric envelopes increases (as one would expect for force free radial outflow). For Halley the integral decreases as one gets closer to the nucleus. Borrelly shows opposite behaviour. The main cause for Halley's intensity distribution is either high optical thickness or particle fragmentation. For Borrelly, we have constructed a simple model of the brightness distribution near the nucleus. This indicates that the influence of deviations from point source geometry is insufficient to explain the observed steepening of the intensity profile close to the nucleus. Dust acceleration or fragmentation into submicron particles appear to be required. We also estimate the dust production rate of Borrelly with respect to Halley and compare their dust to gas ratios.
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Title: |
|
The HNC/HCN ratio in comets: Observations of C/2002 C1 (Ikeya-Zhang) |
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Authors: |
|
Rodgers, S. D.; Butner, H. M.; Charnley, S. B.; Ehrenfreund, P. |
|
Affiliation: |
|
AA(Space Science Division, MS 245-3, NASA Ames Research Center, Mofett Field, CA 94035, USA; rodgers@dusty.arc.nasa.gov), AB(SMTO-Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721, USA), AC(Space Science Division, MS 245-3, NASA Ames Research Center, Mofett Field, CA 94035, USA), AD(Leiden Observatory, PO Box 9513, 2300 RA Leiden, The Netherlands) |
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Journal: |
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Advances in Space Research, Volume 31, Issue 12, p. 2577-2582. (AdSpR Homepage) |
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Publication Date: |
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06/2003 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
|
(c) 2003 Elsevier Science B.V. All rights reserved. |
|
DOI: |
|
|
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Bibliographic Code: |
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2003AdSpR..31.2577R |
We have observed HNC and HCN in the coma of comet C/2002 C1 (Ikeya-Zhang). We derive HNC/HCN ratios of 23 per cent and 3 percent at heliocentric distances of 0.73 and 0.96 AU respectively. These amounts of HNC cannot be synthesised in the coma via bimolecular chemical reactions, and so these observations appear to confirm that the dominant source of HNC in cometary comae is the degradation of complex organic material.
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Title: |
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Remote infrared observations of parent volatiles in comets: A window on the early solar system |
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Authors: |
|
Mumma, M. J.; Disanti, M. A.; dello Russo, N.; Magee-Sauer, K.; Gibb, E.; Novak, R. |
|
Affiliation: |
|
AA(; Mumma@nasa.gov), AB(Laboratory for Extraterrestrial Physics, code 690, NASA GSFC, Greenbelt, MD 20771 USA), AC(Catholic University of America, code 690.2, NASA GSFC, Greenbelt, MD 20771 USA), AD(Dept. of Chemistry and Physics, Rowan University, Glassboro, NJ 08028-1701 USA), AE(NAS-NRC code 690.2, NASA GSFC, Greenbelt, MD 20771 USA), AF(Dept. of Physics, Iona College, New Rochelle, NY 10801-1830 USA) |
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Journal: |
|
Advances in Space Research, Volume 31, Issue 12, p. 2563-2575. (AdSpR Homepage) |
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Publication Date: |
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06/2003 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
|
(c) 2003 Elsevier Science B.V. All rights reserved. |
|
DOI: |
|
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Bibliographic Code: |
|
2003AdSpR..31.2563M |
Organic volatiles and water in Oort
Cloud comets were investigated at infrared wavelengths. The detected species
include H2O, CO, CH3OH, CH4, C2H2,
C2H6, OCS, HCN, NH3, and H2CO.
Several daughter fragments (
|
Title: |
|
A quantitative model for comet nucleus topography |
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Authors: |
|
|
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Affiliation: |
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AA(Southwest Research Institute, P. O. Drawer 28510, |
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Journal: |
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Advances in Space Research, Volume 31, Issue 12, p. 2555-2562. (AdSpR Homepage) |
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Publication Date: |
|
06/2003 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
|
(c) 2003 Elsevier Science B.V. All rights reserved. |
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DOI: |
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Bibliographic Code: |
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2003AdSpR..31.2555H |
Topography of the surface of a comet nucleus is likely rough at all scales smaller than the mean effective radius. We present a flexible and easily scalable model for quantitative calculations simulating the effects of comet nucleus topography on gas release and dust mantle evolution. The topographic features we describe must be large enough (typically > 10 m) so that they will not erode in one orbit of the nucleus around the Sun. The maximum effective size of a hill is about 1/√2 times the effective radius of the nucleus. If it is larger, then an ellipsoidal shape of the nucleus is more appropriate. The procedure described here also permits for inhomogeneous composition of the topographic features, leading to locally different rates of gas production (e.g., jet-like features and filaments) or different thicknesses of the dust mantle. It also can give rise to different temperature patches, locally varying albedos and emissivities, and may explain the formation of permanent dust mantles.
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Title: |
|
Modelling of cometary nuclei: Planetary missions preparation |
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Authors: |
|
|
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Affiliation: |
|
AA(IASF-CNR,
Area di Ricerca di Tor Vergata, via del Fosso del Cavaliere, 00133 Rome,
Italy; capria@ias.rm.cnr.it), AB(IFSI-CNR, Area di Ricerca di Tor Vergata,
via del Fosso del Cavaliere, 00133 Rome, Italy), AC(IASF-CNR, Area di Ricerca
di Tor Vergata, via del Fosso del Cavaliere, 00133 Rome, Italy) |
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Journal: |
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Advances in Space Research, Volume 31, Issue 12, p. 2543-2553. (AdSpR Homepage) |
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Publication Date: |
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06/2003 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
|
(c) 2003 Elsevier Science B.V. All rights reserved. |
|
DOI: |
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Bibliographic Code: |
|
2003AdSpR..31.2543C |
The planning of planetary missions requires the knowledge as much as possible accurate of the target. This knowledge, which cannot be obtained only by ground based observations, can be supported by theoretical modeling. This is particularly true in the case of Rosetta, a cornerstone ESA mission that will be launched in January 2003, and of its target, the comet 46P/Wirtanen. In this paper we show how, using a nucleus thermal evolution model, it is possible to foresee the temperature of the nucleus surface and the activity level along the orbit and define the range of possible values for these properties. Activity level close to the aphelion depends on the presence of CO. Surface temperatures depend on the physical properties attributed to the dust: temperatures reached by a crust mainly composed by silicatic grains differ from the temperatures reached by a crust mainly composed by organic grains.
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Title: |
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Models of P/Borrelly: Activity and dust mantle formation |
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Authors: |
|
|
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Affiliation: |
|
AA(Istituto di
Astrofisica Spaziale e Fisica Cosmica, CNR, via del Fosso del Cavaliere 100,
0133 Roma, Italy; cristina@ias.rm.cnr.it), AB(Istituto di Astrofisica Spaziale e
Fisica Cosmica, CNR, via del Fosso del Cavaliere 100, 0133 Roma, Italy; capria@ias.rm.cnr.it), AC(Istituto di Fisica dello Spazio
Interplanetario, CNR, via del Fosso del Cavaliere 100, 0133 Roma, Italy; coradini@ias.rm.cnr.it) |
|
Journal: |
|
Advances in Space Research, Volume 31, Issue 12, p. 2519-2525. (AdSpR Homepage) |
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Publication Date: |
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06/2003 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
|
(c) 2003 Elsevier Science B.V. All rights reserved. |
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DOI: |
|
|
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Bibliographic Code: |
|
2003AdSpR..31.2519D |
Comet 19P/Borrelly was observed by Deep Space One spacecraft on September 22, 2001 (Soderblom et al., 2002).The DS1 images show a very dark and elongate nucleus with a complex topography; the IR spectra show a strong red-ward slope consistent with a very hot and dry surface (345K to 300K). During DS1 encounter the comet coma was dominated by a prominent jet but most of the comet was inactive, confirming the Earth-based observations that <10% of the surface is actively sublimating. We have developed a thermal evolution model of comet PBorrelly, using a numerical code that is able to solve the heat conduction and gas diffusion equations at the same time across an idealized spherical nucleus ( De Sanctis et al., 1999, 2000; Capria et al., 2000; Coradini et al., 1997a,b). The comet nucleus is composed by water, volatiles ices and dust in different proportions. The refractory component is made by grains that are embedded in the icy matrix. The code is able to account for the dust release, contributing to the dust flux, and the formation of dust mantles on the comet surface. The model was applied to a cometary nucleus with the estimated physical and dynamical characteristics of P/Borrelly in order to infer the status and activity level of a body on such an orbit during the DS1 observation. The comet gas flux, differentiation and thermal behavior were simulated and reproduced. The model results are in good agreement with the DS1 flyby results and the ground based observations, in terms of activity, dust coverage and temperatures of the surface.
|
Title: |
|
Polarization imaging of dust cloud particles: Improvements and applications of the PROGRA2 instrument |
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Authors: |
|
Renard, J.-B.; Hadamcik, E.; Lemaire, T.; Worms, J.-C.; Levasseur-Regourd, A.-C. |
|
Affiliation: |
|
AA(LPCE-CNRS, 3A avenue de la recherche scientifique, F-45071 Orléans cedex 2, France; jbrenard@cnrs-orleans.fr), AB(Service d'Aéronomie du CNRS-IPSL, BP 3, F-91371 Verrières le Buisson cedex, France), AC(LPCE-CNRS, 3A avenue de la recherche scientifique, F-45071 Orléans cedex 2, France), AD(ESSC c/o ENSPS - parc d'innovation, boulevard Sébastien Brandt, F-674121 Ilkirch cedex France), AE(Service d'Aéronomie du CNRS-IPSL, BP 3, F-91371 Verrières le Buisson cedex, France) |
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Journal: |
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Advances in Space Research, Volume 31, Issue 12, p. 2511-2518. (AdSpR Homepage) |
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Publication Date: |
|
06/2003 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
|
(c) 2003 Elsevier Science B.V. All rights reserved. |
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DOI: |
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Bibliographic Code: |
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2003AdSpR..31.2511R |
The imaging system of the -PROGRA2 instrument allows to obtain maps of polarization and brightness of levitating dust clouds with a theoretical resolution of 10 μm per pixel. The measurements are conducted in microgravity during parabolic flights and on the ground by air-draught. It is then possible to measure the contribution of individual particles (grains, aggregates and agglomerates.) The size distribution can be retrieved, as well as the variation of polarization for a given phase angle with size for particles larger than 10 microns. Two different kinds of particles are considered: compact grains and (aggregates and agglomerates of) fluffy particles. Opposite results are obtained for these two kinds of particles, concerning the dependence of polarization with size and color in the visible domain for gray materials. These results, coupled with such remote sensing observations in the solar system, can then help to better understand the physical properties of solid particles and their variation in cometary comae, as well as in the Earth's atmosphere.
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Title: |
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Numerical simulations of the radiance from the comet 46P/Wirtanen in the various configurations of the measurements during ``Rosetta'' mission |
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Authors: |
|
Blecka, M. I.; Capria, M. T.; Coradini, A.; de Sanctis, M. C. |
|
Affiliation: |
|
AA(Space
Research Centre, Polish Academy of Sciences, Bartycka 18A, 00-716 Warszawa,
Poland; mib@cbk.waw.pl), AB(IASF - CNR Via del Fosso del Cavaliere, 00133
Rome, Italy), AC(IFSI - CNR Via del Fosso del Cavaliere, 00133 Rome, Italy),
AD(IASF - CNR Via del Fosso del Cavaliere, 00133 Rome, Italy) |
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Journal: |
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Advances in Space Research, Volume 31, Issue 12, p. 2501-2510. (AdSpR Homepage) |
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Publication Date: |
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06/2003 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
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(c) 2003 Elsevier Science B.V. All rights reserved. |
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DOI: |
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Bibliographic Code: |
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2003AdSpR..31.2501B |
The work we present deals with the spectrometric measurements of VIRTIS instrument of the Comet P/Wirtanen planned for the Rosetta mission. This spectrometer can monitor (VIRTIS M channel: 0.250μm - 0.980μm Δκ=20cm-1 0.980 - 5.0 μm Δκ = 5cm-1 VIRTIS H channel: 2.0 μm - 5.0 μm Δκ=2cm-1) the nucleus and the coma in order to provide a general picture of coma's composition, the production of gas and dust, the relationship of coma production to surface composition and the structure and variation of mineralogy of the nucleus surface. During the mission the observation conditions of the spectroscopic investigation change due to different relative positions spacecraft/comet, and to the different illumination conditions of the surface at various distances of the comet to the Sun. The nucleus surface is continuously modified by the ice sublimation accompanied by gas and dust emission. Consequently the surface also its spectrophotometric properties changes and their monitoring can give a new insight. The important role of simulations is to predict the results of measurements in various experimental condition what, in the future, can help in interpretation of the measured data.
In this paper the first results of our simulation the radiance from the comet in the 0.25-5.0μm spectral range at two distances from the Sun (~1AU and ~3AU) are shown. The distance between the Rosetta orbiter and the nucleus surface as well as the sun zenith angles are taken into account according to the Rosetta mission phases. In fact the surface and coma properties vary along the comet orbit, and should be taken into account in our calculations. The optical parameters of the dust on the surface (e.g. reflectance) and in the coma (e.g. Qext) were calculated from optical constants of possible comet analogues. The thermodynamic parameters of the comet are taken from the models of comet evolution. Through this kind of modelling it is possible to identify the surface characteristics in spectra of the radiation from the surface of nucleus transmitted through the coma loaded with dust and gases.
Even if the ``Rosetta mission'' is postponed, with the consequence of a target change, we think that our idea and the method used for the simulations can be useful also for the new Rosetta target - the comet 67P/Churyumov Gerasimenko.
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Title: |
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Dust in comet McNaught-Hartley (C/1999 T1) from Jan. 25 to Feb. 04, 2001: IR and optical CCD imaging |
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Authors: |
|
|
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Affiliation: |
|
AA(Instituto de
Astrofísica de Andalucía, CSIC, Camino Bajo de Huétor 24, 18008 Granada,
Spain), AB(Isaac Newton Group of Telescopes & Instituto de Astrofísica de
Canarias, PO Box 321, 38700 Santa Cruz de La Palma, Tenerife, Spain licandro@ing.iac.es ), AC(INAF-Osservatorio Astrofisico di Arcetri,
Largo E. Fermi 5, 50125, Firenze, Italy tozzi@arcetri.astro.it) |
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Journal: |
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Astronomy and Astrophysics, v.404, p.373-378 (2003) (A&A Homepage) |
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Publication Date: |
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06/2003 |
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Origin: |
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A&A |
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A&A Keywords: |
|
comets: individual: McNaught-Hartley (C/1999 T1), comets: general |
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DOI: |
|
|
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Bibliographic Code: |
|
2003A&A...404..373L |
Broad-band optical and infrared observations in the R, I, and J, H, Ks bands of comet McNaught-Hartley (C/1999 T1) were performed from Jan. 25 to Feb. 4, 2001, shortly after the comet perihelion on Dec. 14, 2000. For the time the comet was observed, it did not show any peculiar behaviour either in the infrared or in the optical, that is, no non-spherical structures, besides the dust tail, or outburst or daily activity variations were detected. Calibration of the images in the A f rho frame provide us with values of dust production between 1000 and 3000 cm, depending on the date and on the wavelength. The general behaviour of the dust coma of C/1999 T1 is that described by a steady-state production of long-lived grains expanding radially outwards from the nucleus. The dust color does not clearly change with projected cometocentric distance. During a time span of 10 days, the cometary dust grains observed in the Ks filter seemed to become slightly redder on Feb. 05 than they were on Jan. 26, 2001.
|
Title: |
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SOHO/LASCO observation of an outburst of Comet 2P/Encke at its 2000 perihelion passage |
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Authors: |
|
|
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Affiliation: |
|
AA(Laboratoire d'Astronomie Spatiale, C.N.R.S., BP8, 13376
12, Marseille |
|
Journal: |
|
Icarus, Volume 163, Issue 1, p. 142-149. (Icarus Homepage) |
|
Publication Date: |
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05/2003 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
|
(c) 2003 Elsevier Science ( |
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DOI: |
|
|
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Bibliographic Code: |
|
2003Icar..163..142L |
Comet 2P/Encke was observed with the SOHO/LASCO C2 and C3 coronagraphs over a time interval of 11 days, starting 4 days before its September 2000 perihelion passage and through several broadband visible filters. The lightcurve reveals an outburst which started 4.9 days after perihelion, with the brightness of the coma increasing by 1.5 mag in just a few hours and progressively decreasing thereafter, probably going back to its original state in about 9 days. The color information indicates that an approximately solar color continuum was detected, implying that the observed signals were dominated by solar light scattered off submillimetric dust grains. We propose that the rapid migration of the subsolar point over the southern hemisphere during the perihelion passage activates one or several new active regions enriched in submillimetric grains, with the observed outburst corresponding to the initial blow-off of their mantle. This scenario is consistent with other observations and implies that the south polar region of the nucleus of 2P/Encke has very distinct properties.
|
Title: |
|
Deep Space 1 encounter with Comet 19P/Borrelly: Ion composition measurements by the PEPE mass spectrometer |
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Authors: |
|
Nordholt, J. E.; Reisenfeld, D. B.; Wiens, R. C.; Gary, S. P.; Crary, F.; Delapp, D. M.; Elphic, R. C.; Funsten, H. O.; Hanley, J. J.; Lawrence, D. J.; McComas, D. J.; Shappirio, M.; Steinberg, J. T.; Wang, J.; Young, D. T. |
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Journal: |
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Geophysical Research Letters, Volume 30, Issue 9, pp. 18-1, CiteID 1465, DOI 10.1029/2002GL016840 (GeoRL Homepage) |
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Publication Date: |
|
05/2003 |
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Origin: |
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AGU |
|
AGU Keywords: |
|
Planetology: Comets and Small Bodies: Atmospheres-composition and chemistry, Planetology: Comets and Small Bodies: Interactions with solar wind plasma and fields, Planetology: Comets and Small Bodies: Composition |
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Abstract Copyright: |
|
(c) 2003: American Geophysical |
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DOI: |
|
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Bibliographic Code: |
|
2003GeoRL..30i..18N |
We report in situ ion mass spectrometer measurements from the coma of Comet 19P/Borrelly, obtained during the flyby of the Deep Space 1 spacecraft on 22 September 2001. Cometary ions were detected at distances from ~5.5 × 105 km to 2200 km from the nucleus of the comet. The predominant heavy ions observed during the seven minute interval about closest approach to Borrelly included OH+ (at 57% of the total water-group ion density), H2O+ (at 29%), O+ (at 13%), CH3+ (at 5%), and CH2+ (at 4%). Of particular note is the small amount of H3O+ (<9%), as this was the most abundant molecular ion observed at closest approach to Comet Halley. This difference is due to the difference in water production rates between the two comets.
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Title: |
|
Dust evolution of comet C/1995 O1 (Hale-Bopp) by imaging polarimetric observations |
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Authors: |
|
|
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Affiliation: |
|
AA(Service d'Aéronomie/CNRS, BP 3, 91371 |
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Journal: |
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Astronomy and Astrophysics, v.403, p.757-768 (2003) (A&A Homepage) |
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Publication Date: |
|
05/2003 |
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Origin: |
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A&A |
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A&A Keywords: |
|
comets: individual: C/1995 01 (Hale-Bopp), polarization, scattering, ISM: dust, extinction, techniques: polarimetric |
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DOI: |
|
|
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Bibliographic Code: |
|
2003A&A...403..757H |
Comet C/1995 O1 (Hale-Bopp) has been observed over a large range of phase angles (7deg-47deg) by the imaging polarimetric method from June 1996 to April 1997. Polarization maps were obtained and long-term evolution (month) of the coma structures followed. Short-term evolution (20 min) during the April 1997 observations has allowed us to measure the period of rotation of the central arc on the polarization maps. The comparison between the polarization maps and the intensity structures confirms a greater polarization in the jets. Phase curves are obtained for different regions of the coma and compared to those obtained for the whole coma. For the region around the nucleus, the phase curve is always underneath the phase curve corresponding to the whole coma, and the polarization at phase angles smaller than 25deg is negative (Pmin = -5%). In the jets, the phase curve is always above the whole coma phase curve, and the polarization is always positive. Whole coma phase curves are obtained with all the available data sets in different wavelengths. A comparison with other diagnostics and laboratory experiments leads us to suggest that small grains build up fluffy aggregates of high porosity; the light scattered by such aggregates is highly polarized, as observed in this active comet.
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Title: |
|
The dust activity of comet C/1995 O1 (Hale-Bopp) between 3 AU and 13 AU from the Sun |
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Authors: |
|
Weiler, M.; Rauer, H.; Knollenberg, J.; Jorda, L.; Helbert, J. |
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Affiliation: |
|
AA(Institute of Space Sensor Technology and Planetary Exploration, DLR, Rutherfordstrasse 2, 12489 Berlin, Germany), AB(Institute of Space Sensor Technology and Planetary Exploration, DLR, Rutherfordstrasse 2, 12489 Berlin, Germany), AC(Institute of Space Sensor Technology and Planetary Exploration, DLR, Rutherfordstrasse 2, 12489 Berlin, Germany), AD(Laboratoire d'Astrophysique de Marseille, Site Pereisc, 13376 Marseille Cedex 12, France), AE(Institute of Space Sensor Technology and Planetary Exploration, DLR, Rutherfordstrasse 2, 12489 Berlin, Germany) |
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Journal: |
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Astronomy and Astrophysics, v.403, p.313-322 (2003) (A&A Homepage) |
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Publication Date: |
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05/2003 |
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Origin: |
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A&A |
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A&A Keywords: |
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comets: general, comets: individual: Hale-Bopp |
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DOI: |
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|
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Bibliographic Code: |
|
2003A&A...403..313W |
The active comet C/1995 O1 (Hale-Bopp) was target of an optical long-term monitoring program carried out at the European Southern Observatory (ESO) (Rauer et al. \cite{rauer}, \cite{rauer:02}). Longslit spectra and images were obtained at heliocentric distances from 4.6 AU to 2.9 AU preperihelion and 2.8 AU to 12.8 AU postperihelion. Based on these data, the dust activity of comet Hale-Bopp is analysed. The color of the dust coma and the Afrho parameter are determined. A model for the dust release from the cometary nucleus is presented and used to compute dust production rates. The dust to gas ratio is determined.
Based on observations collected at the European Southern Observatory, Chile.
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Title: |
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Observations of water in comets with Odin |
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Authors: |
|
Lecacheux, A.; Biver, N.; Crovisier, J.; Bockelée-Morvan, D.; Baron, P.; Booth, R. S.; Encrenaz, P.; Florén, H.-G.; Frisk, U.; Hjalmarson, Å.; Kwok, S.; Mattila, K.; Nordh, L.; Olberg, M.; Olofsson, A. O. H.; Rickman, H.; Sandqvist, Aa.; von Schéele, F.; Serra, G.; Torchinsky, S.; Volk, K.; Winnberg, A. |
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Affiliation: |
|
AA(Observatoire de Paris, FRE 2461 du CNRS, Place Jules Janssen, 92195 Meudon, France, ), AB(Observatoire de Paris, FRE 2461 du CNRS, Place Jules Janssen, 92195 Meudon, France, ; ESA-ESTEC Keplerlaan 1, 2200 AG, Noordwijk, The Netherlands), AC(Observatoire de Paris, FRE 2461 du CNRS, Place Jules Janssen, 92195 Meudon, France, ), AD(Observatoire de Paris, FRE 2461 du CNRS, Place Jules Janssen, 92195 Meudon, France, ), AE(Observatoire de Paris, FRE 2461 du CNRS, Place Jules Janssen, 92195 Meudon, France; Noveltis, Parc Technologique du canal, 2 avenue de l'Europe, 31520 Ramonville Saint Agne, France), AF(Onsala Space Observatory, 439 92 Onsala, Sweden), AG(Observatoire de Paris, FRE 2460 du CNRS, 61 Av. de l'Observatoire, 75014 Paris, France), AH(Stockholm Observatory, SCFAB-Albanova, 106 91 Stockholm, Sweden), AI(Swedish Space Corporation, Box 4207, 171 04 Solna, Sweden), AJ(Onsala Space Observatory, 439 92 Onsala, Sweden), AK(Dept. of Physics and Astronomy, University of Calgary, Calgary, AB T2N 1N4, Canada), AL(Observatory, PO Box 14, Tähtitorninmäki, University of Helsinki, 00014 Helsinki, Finland), AM(Swedish National Space Board, Box 4006, 171 04 Solna, Sweden), AN(Onsala Space Observatory, 439 92 Onsala, Sweden), AO(Onsala Space Observatory, 439 92 Onsala, Sweden), AP(Uppsala Astronomical Observatory, Box 515, 751 20 Uppsala, Sweden), AQ(Stockholm Observatory, SCFAB-Albanova, 106 91 Stockholm, Sweden), AR(Swedish Space Corporation, Box 4207, 171 04 Solna, Sweden), AS(CESR, 9 Avenue du Colonel Roche, BP 4346, 31029 Toulouse, France), AT(Canadian Space Agency, St-Hubert, Québec J3Y 8Y9, Canada), AU(Observatoire de Paris, FRE 2460 du CNRS, 61 Av. de l'Observatoire, 75014 Paris, France), AV(Onsala Space Observatory, 439 92 Onsala, Sweden) |
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Journal: |
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Astronomy and Astrophysics, v.402, p.L55-L58 (2003) (A&A Homepage) |
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Publication Date: |
|
05/2003 |
|
Origin: |
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A&A |
|
A&A Keywords: |
|
comets: general, comets: individual: C/2001 A2 (LINEAR), 19P/Borrelly, C/2000 WM1 (LINEAR), 153P/2002 C1 (Ikeya-Zhang), radio lines: solar system, submillimeter |
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DOI: |
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Bibliographic Code: |
|
2003A&A...402L..55L |
The Odin satellite, which can observe the 110-101 rotational line at 557 GHz of ortho water with a high spectral resolution (80 m s-1) and a spatial resolution of 2.1\arcmin, is well suited for cometary studies. The intensity of this line provides an estimate of the water production rate. The line width gives a direct measure of the coma expansion velocity. The line centre position and shape are affected by the anisotropy of the outgassing and by optical depth effects. Comets observed with Odin up to now are C/2001 A2 (LINEAR) during the commissioning phase of the satellite, 19P/Borrelly at the time of the Deep Space 1 flyby, C/2000 WM1 (LINEAR), and 153P/2002 C1 (Ikeya-Zhang). For this last comet, thorough observations were made at the moment of its closest approach to Earth at the end of April 2002. A deep integration resulted in the detection of the 110-101 line of H218O at 548 GHz. No 16O/18O isotopic anomaly is found.
Odin (http://www.snsb.se/eng_odin_team.shtml) is a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and the Centre National d'Études Spatiales (CNES, France). The Swedish Space Corporation is the prime contractor, also responsible for Odin operations.
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Title: |
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The possibility of stable location of dust grains in a comet atmosphere |
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Authors: |
|
|
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Journal: |
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Kinematika i
Fizika Nebesnykh Tel, vol. 19, no. 2, p. 138-158 |
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Publication Date: |
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04/2003 |
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Origin: |
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KFNT |
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Language: |
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Russian |
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Bibliographic Code: |
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2003KFNT...19..138A |
The possibility of stable location of dust grains in a comet atmosphere with weak dust content is studied on the basis of the simulation of the hydrodynamical spherically symmetric gas flow, if Knudsen boundary layer of a comet nuclear is taken into account, at heliocentric distances from 1.6 to 3.0 a.u. We consider two types of surface sublimation, namely, a clean homogeneous surface of water ice and that covered by a porous mineral crust. With the use of the phase plane method it is shown that there are two specific points in a comet atmosphere for centimetre-sized dust particles and one of the points is a point of stable equilibrium. A relationship between this point position and dust grain sizes is found. Variations of the density and shape of grains as well as the size distribution result in initiation of a stable equilibrium zone. Its location depends on the size of a comet, distance of a comet from the Sun, and the state of the nuclear surface of a comet. For comets of size 2.5 km at 2 a.u., this zone is positioned at distances from 10 to 1000 km and corresponds to the dust grains of size from 4.5 down to 0.5 cm and of density 1 g/cm3.
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Title: |
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Extreme ultraviolet photolysis of CO2 - H2O mixed ices at 10 K |
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Authors: |
|
Wu, C. Y. Robert; Judge, D. L.; Cheng, Bing-Ming; Yih, Tai-Sone; Lee, C. S.; Ip, W. H. |
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Journal: |
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Journal of Geophysical Research (Planets), Volume 108, Issue E4, pp. 13-1, CiteID 5032, DOI 10.1029/2002JE001932 (JGRE Homepage) |
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Publication Date: |
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04/2003 |
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Origin: |
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AGU |
|
AGU Keywords: |
|
Planetology: Fluid Planets: Surfaces, Planetology: Comets and Small Bodies: Composition, Planetology: Comets and Small Bodies: Physics and chemistry of materials, Planetology: Comets and Small Bodies: Radiation and spectra, |
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Abstract Copyright: |
|
(c) 2003: American Geophysical |
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DOI: |
|
|
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Bibliographic Code: |
|
2003JGRE.108d...13W |
Experimental results on the spectral identification of IR absorption features and the production and depletion column densities produced through EUV photolysis of H2O + CO2 (4:1) mixed ices at 10 K are reported. A tunable intense synchrotron radiation light source was employed to provide the required high flux EUV photons. In this study the photon wavelengths used to irradiate the icy sample were selected to coincide with the prominent solar lines at 58.4 nm and 30.4 nm. A FTIR spectrometer was employed to obtain the in situ IR absorbance spectra produced through EUV photolysis of a given ice sample. Photon-induced chemical reaction products were primarily H2CO3 and CO. While new molecular species were formed, the original reactants were depleted, as expected. We report the yields for producing H2CO3 and CO and the yields for depleting the parent CO2 molecule through EUV photolysis of the mixed ices. We have searched for possible intermediate products H2CO and HCO, but could not positively identify their existences in the spectra. The results presented in this work are particular relevant to our understanding of chemical evolution and synthesis in H2O-rich icy satellites of the giant planets, comets, the interstellar medium, molecular clouds, and protostellar regions.
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Title: |
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Comet 19P/Borrelly at multiple apparitions: seasonal variations in gas production and dust morphology |
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Authors: |
|
|
|
Affiliation: |
|
AA(Lowell Observatory, 1400 W. Mars Hill Road, 86001, Flagstaff, AZ, USA), AB(Lowell Observatory, 1400 W. Mars Hill Road, 86001, Flagstaff, AZ, USA), AC(Lowell Observatory, 1400 W. Mars Hill Road, 86001, Flagstaff, AZ, USA) |
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Journal: |
|
Icarus, Volume 162, Issue 2, p. 415-442. (Icarus Homepage) |
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Publication Date: |
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04/2003 |
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Origin: |
|
ELSEVIER |
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Abstract Copyright: |
|
(c) 2003 Elsevier Science ( |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2003Icar..162..415S |
We present analysis and results from both narrowband photometry and CCD imaging of Comet 19P/Borrelly from multiple apparitions. Production rates for Borrelly a few days prior to the Deep Space 1 spacecraft encounter were Q(OH) = 2.1×1028 molecule s-1, Q(CN) = 5.1×1025 molecule s-1, and A(θ)fρ = 400-500 cm. The equivalent Q(water; vectorial) = 2.5×1028 molecule s-1. We also find that the radial fall-off of the dust is significantly steeper than the canonical 1/ρ for aperture sizes larger than ρ = 2×104 km. In the near-UV, a strong trend in dust colors with aperture size is present. Imaging of Borrelly revealed a strong radial jet in the near-sunward direction that turns off late in the apparition. For the jet to appear radial, it must originate at or very close to the nucleus' pole. Modeling the measured position angle of this jet as a function of time during the 1994 and 2001 apparitions yields a nucleus in a simple, rather than complex, rotational state with a pole orientation having an obliquity of 102.7° +/- 0.5° and an orbital longitude of the pole of 146° +/- 1°, corresponding to an RA of 214.1° and a Declination of -5.7° (J2000). There is also evidence for a small (~8°) precession of the pole over the past century, based on our preferred model solution for jet measurements obtained during the 1911-1932 apparitions. Our solution for the orientation of the rotation axis implies a very strong seasonal effect as the source region for the jet moves from summer to winter. This change in solar illumination quantitatively explains both the nearly level water production measured in the seven weeks preceding perihelion and the extremely large decrease in water production (25×) as Borrelly moved from perihelion to 1.9 AU. A much smaller fall-off in apparent dust production after perihelion can be explained by a population of old, very slowly moving large grains released near peak water production, and therefore not indicative of the actual ongoing release of dust grains late in the apparition. Based on the water vaporization rate, the source region has an area of approximately 3.5 km2 or 4% of the total surface area of the nucleus, and water ice having an effective depth of 3-10 m is released each apparition from this source region.
|
Title: |
|
An S2 Fluorescence Model for Interpreting High-Resolution Cometary Spectra. I. Model Description and Initial Results |
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Authors: |
|
|
|
Affiliation: |
|
AA(Observatoire de Besançon, BP 1615, 25010 |
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Journal: |
|
The Astrophysical Journal, Volume 587, Issue 1, pp. 464-471. (ApJ Homepage) |
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Publication Date: |
|
04/2003 |
|
Origin: |
|
UCP |
|
ApJ Keywords: |
|
Comets: General, Molecular Processes, Ultraviolet: Solar System |
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Abstract Copyright: |
|
(c) 2003: The American Astronomical Society |
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DOI: |
|
|
|
Bibliographic Code: |
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2003ApJ...587..464R |
A new versatile model providing S2 fluorescence spectrum as a function of time is developed with the aim of interpreting high-resolution cometary spectra. For the S2 molecule, it is important to take into account both chemical and dynamic processes because S2 has a short lifetime and is confined in the inner coma, where these processes are most important. The combination of the fluorescence model with a global coma model allows for the comparison with observations of column densities taken through an aperture and for the analysis of S2 fluorescence in different parts of the coma. Moreover, the model includes the rotational structure of the molecule. Such a model is needed for interpreting recent high spectral resolution observations of cometary S2. A systematic study of the vibrational-rotational spectrum of S2 is undertaken, including relevant effects, such as nonequilibrium state superposition and the number density profile within the coma due to dynamics and chemistry, to investigate the importance of the above effects on the scale length and abundance of S2 in comets.
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Title: |
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Production and kinematics of CO in comet C/1995 O1 (Hale-Bopp) at large post-perihelion distances |
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Authors: |
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Gunnarsson, M.; Bockelée-Morvan, D.; Winnberg, A.; Rickman, H.; Crovisier, J.; Biver, N.; Colom, P.; Davies, J. K.; Despois, D.; Henry, F.; Johansson, L. E. B.; Moreno, R.; Paubert, G.; Rantakyrö, F. T. |
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Affiliation: |
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AA(Astronomiska Observatoriet, Box 515, 75120 Uppsala, Sweden), AB(Observatoire de Paris, 92195 Meudon, France), AC(Onsala Space Observatory, Sweden), AD(Astronomiska Observatoriet, Box 515, 75120 Uppsala, Sweden), AE(Observatoire de Paris, 92195 Meudon, France), AF(European Space Agency, ESTEC Sci-So, Noordwijk, The Netherlands), AG(Observatoire de Paris, 92195 Meudon, France), AH(Joint Astronomy Centre, Hilo, HI, USA), AI(Observatoire de Bordeaux, France), AJ(Observatoire de Paris, 92195 Meudon, France), AK(Onsala Space Observatory, Sweden), AL(Institut de Radio Astronomie Millimétrique, Grenoble, France), AM(Institut de Radio Astronomie Millimétrique, Granada, Spain), AN(European Southern Observatory, Casilla 19001, Santiago 19, Chile; Observatorio Cerro Calan, Universidad de Chile, Santiago, Chile) |
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Journal: |
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Astronomy and Astrophysics, v.402, p.383-393 (2003) (A&A Homepage) |
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Publication Date: |
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04/2003 |
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Origin: |
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A&A |
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A&A Keywords: |
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comets: individual: C/1995 O1 (Hale-Bopp), radio lines: solar system |
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DOI: |
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Bibliographic Code: |
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2003A&A...402..383G |
Radio observations of different molecular species in comet C/1995 O1(Hale-Bopp) have been carried out regularly since August 1995. We present an analysis of carbon monoxide spectra observed at SEST. A detailed picture of the nature of the post-perihelion outgassing at large heliocentric distances is shown. The data starts at 2.9 AU, with active water sublimation, and stretch outside 10 AU, where CO-driven activity is still detected. The activity is studied using a coma model which separates the outgassing into two different sources, one insolation-dependent source, peaking at the subsolar point, and one isotropically outgassing source. Gas velocities and production rates of the two sources are derived for two different cases. In the first case the isotropic source is assumed to be inside the nucleus, and in the second case this source is assumed to be CO-rich material in the coma. Under both assumptions, the results indicate that the two component sources evolve independently. At heliocentric distances around 3 AU, acceleration of the CO molecules in the innermost region of the coma is required for the model to fit the observations. This acceleration must occur at a slower rate than that predicted by hydrodynamic simulations. From 6 to 10 AU, the derived parameters appear remarkably constant. The nuclear outgassing velocity is generally unchanged with heliocentric distance during this wide interval. Observations of molecules other than CO are included in the SEST dataset, and a comparison is made to the modelling results. HCN and CH3OH show signs of being produced in the same way as the CO up to a heliocentric distance of 6 AU.
Based on results collected at the European
Southern Observatory, La Silla,
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Title: |
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An investigation of errors in estimates of the cometary nuclei active area fractions |
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Authors: |
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Gutiérrez, P. J.; Rodrigo, R.; Ortiz, J. L.; Davidsson, B. J. R. |
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Affiliation: |
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AA(Instituto de Astrofísica de Andalucía, CSIC, Aptd 3004,
18080 |
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Journal: |
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Astronomy and Astrophysics, v.401, p.755-761 (2003) (A&A Homepage) |
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Publication Date: |
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04/2003 |
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Origin: |
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A&A |
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A&A Keywords: |
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comets: general, solar system: general |
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DOI: |
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Bibliographic Code: |
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2003A&A...401..755G |
Active area fractions of cometary nuclei are often estimated by comparing the observed water production rates with theoretical rates obtained by applying the fast rotator or subsolar point approximations to spherical model nuclei. Any discrepancy between observed and theoretical production rates is interpreted as a certain degree of dust mantling (or in some cases hyper activity) of the object. We here investigate the typical errors introduced in such active area fraction estimates by the usage of oversimplified spherical model nuclei. This is done by first calculating the production rates of slowly rotating irregular model bodies with different activity patterns on their surfaces and arbitrary spin axis orientations, for which solar illumination is treated properly. Next, the production rates of the spherical model objects under averaged insolation are compared to the production rates of the complex model objects in an attempt to recover the known active area fraction of the latter bodies. We then find that the fast rotator and subsolar point approximations generally yield large over- and underestimates of the active area fraction, depending on the characteristics of the simulated complex nuclei. Acceptable relative errors (<100%) only occur at small heliocentric distances, and the subsolar point approximation yields somewhat better results than the fast rotator approximation.
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Title: |
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The origin of crystalline silicates in the Herbig Be star HD 100546 and in comet Hale-Bopp |
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Authors: |
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Affiliation: |
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AA(Astronomical Institute ``Anton Pannekoek'', University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands; CEA, DSM, DAPNIA, Service d'Astrophysique, CE Saclay, 91191 Gif-sur-Yvette Cedex, France), AB(Astronomical Institute ``Anton Pannekoek'', University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands), AC(Astronomical Institute ``Anton Pannekoek'', University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands), AD(Astronomical Institute ``Anton Pannekoek'', University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands; Instituut voor Sterrenkunde, K.U. Leuven, Celestijnenlaan 200 B, 3001 Heverlee, Belgium) |
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Journal: |
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Astronomy and Astrophysics, v.401, p.577-592 (2003) (A&A Homepage) |
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Publication Date: |
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04/2003 |
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Origin: |
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A&A |
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A&A Keywords: |
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circumstellar matter, stars: formation, stars: pre-main-sequence |
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DOI: |
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Bibliographic Code: |
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2003A&A...401..577B |
We have investigated the spatial distribution, and the properties and chemical composition of the dust orbiting HD 100546. This system is remarkably different from other isolated Herbig Ae/Be stars in both the strength of the mid-IR excess and the composition of the circumstellar dust. To explain spectral features and the amount of mid-IR dust emission the presence of a component of small (<10 mu m) grains radiating at ~ 200 K is required, which is not seen in other well investigated Herbig Ae/Be systems. This additional component is inconsistent with a uniform flaring disk model. The fraction of intercepted stellar light that is absorbed and re-emitted in the mid-IR is so large ( ~ 70%) that it requires the disk to be more ``puffed up'' at about 10 AU, where the grains have T ~ 200 K. This may occur if a proto-Jupiter clears out a gap at this distance allowing direct stellar light to produce an extended rim at the far side of the gap. The other remarkable difference with other isolated Herbig Ae/Be systems is the presence of a much larger mass fraction of the crystalline silicate forsterite in the circumstellar dust. We find that the mass fraction of crystalline silicates in HD 100546 increases with decreasing temperature, i.e. with larger radial distances from the central star. This distribution of crystalline dust is inconsistent with radial mixing models where the crystalline silicates are formed by thermal annealing above the glass temperature in the very inner parts of the disk, and are subsequently transported outwards and mixed with amorphous material. We speculate that the formation and spatial distribution of the crystalline dust may be linked to the formation of a proto-Jupiter in the disk around HD 100546. Such a proto-Jupiter could gravitationally stir the disk leading to a collisional cascade of asteroidal sized objects producing small crystalline grains, or it could cause shocks by tidal interaction with the disk which might produce crystalline dust grains through flash heating. As shown by Malfait et al. (\cite{hd100546malfait}), the infrared spectrum of HD 100546 is very similar to that of C/1995 O1 Hale-Bopp (Crovisier et al. \cite{crovisier1997}). Using an identical methodology, we have therefore also studied this solar system comet. Both objects have an almost identical grain composition, but with the important difference that the individual dust species in Hale-Bopp are in thermal contact with each other, while this is not the case in HD 100546. This suggests that if similar processes leading to the dust composition as seen in HD 100546 also occurred in our own solar system, that Hale-Bopp formed after the formation of one or more proto-gas giants.
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Title: |
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Peculiarities of Cometary Light Curves and Outburst Activity |
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Authors: |
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Affiliation: |
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AA(Astronomical Institute, |
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Journal: |
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Solar System Research, v. 37, Issue 2, p. 134-144 (2003). |
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Publication Date: |
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03/2003 |
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Origin: |
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KLUWER |
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Abstract Copyright: |
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(c) 2003 Kluwer Academic Publishers |
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Bibliographic Code: |
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2003SoSyR..37..134F |
We give an overview of the main results of our works on the revision of cometary light curves and on the search for new patterns and features in the evolution of the integrated brightness of comets as they move in circumsolar space. These works revealed several new, previously unknown phenomena in the integrated-brightness variations and outburst activity of comets. Our results supplement and expand the body of observational data that provides a basis for constructing a model of the cometary nucleus and developing a theory of the cometary evolution.
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Title: |
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A quasi-3D model for the evolution of shape and temperature distribution of comet nuclei-application to Comet 46P/Wirtanen |
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Authors: |
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Affiliation: |
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AA(Department of Geophysics and Planetary Sciences, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel; merav2000@speedy.co.il) |
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Journal: |
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New Astronomy, Volume 8, Issue 3, p. 179-189. (NewA Homepage) |
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Publication Date: |
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03/2003 |
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Origin: |
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ELSEVIER |
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Abstract Copyright: |
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(c) 2003 Elsevier Science B.V. All rights reserved. |
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DOI: |
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Bibliographic Code: |
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2003NewA....8..179C |