COMETARY VOLATILES AND THE ORIGIN OF COMETS
- Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)
- Institute for Geophysics and Extraterrestrial Physics, Technische Universitaet Braunschweig, D-38106 Braunschweig (Germany)
- Department of Physics, Kyoto Sangyo University, Kamigamo JP Kita-ku, Kyoto 603-8555 (Japan)
- Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775 (United States)
- Max-Planck-Institut for Solar System Research, Max-Planck-Strasse 2, D-37191 Katlenburg-Lindau (Germany)
- Jet Propulsion Laboratory/Caltech, Pasadena, CA 91109 (United States)
- NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
- Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
- Department of Geological Sciences, Brown University, Providence, RI 02912 (United States)
- Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States)
- Laboratoire d'Astrophysique de Marseille, Universite d'Aix-Marseille and CNRS, UMR7326, 38 rue F. Joliot-Curie, F-13388 Marseille Cedex 13 (France)
We describe recent results on the CO/CO{sub 2}/H{sub 2}O composition of comets together with a survey of older literature (primarily for CO/H{sub 2}O) and compare these with models of the protoplanetary disk. Even with the currently small sample, there is a wide dispersion in abundance ratios and little if any systematic difference between Jupiter-family comets (JFCs) and long-period and Halley-type comets (LPCs and HTCs). We argue that the cometary observations require reactions on grain surfaces to convert CO to CO{sub 2} and also require formation of all types of comets in largely, but not entirely, overlapping regions, probably between the CO and CO{sub 2} snow lines. Any difference in the regions of formation is in the opposite direction from the classical picture with the JFCs having formed closer to the Sun than the LPCs. In the classical picture, the LPCs formed in the region of the giant planets and the JFCs formed in the Kuiper Belt. However, these data suggest, consistent with suggestions on dynamical grounds, that the JFCs and LPCs formed in largely overlapping regions where the giant planets are today and with JFCs on average forming slightly closer to the Sun than did the LPCs. Presumably at least the JFCs passed through the scattered disk on their way to their present dynamical family.
- OSTI ID:
- 22092110
- Journal Information:
- Astrophysical Journal, Vol. 758, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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