Ethane Production and Release in Comet C/1995 O1 Hale–Bopp

✍ Scribed by Neil Dello Russo; Michael J. Mumma; Michael A. DiSanti; Karen Magee-Sauer; Robert Novak

• Book ID: 102967679
• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 687 KB
• Volume: 153
• Category: Article
• ISSN: 0019-1035
• DOI: 10.1006/icar.2001.6678

✦ Synopsis

Ethane (C 2 H 6 ) was detected in Comet C/1995 O1 Hale-Bopp on 13 dates between UT 1996 September 20.3 (R h = 3.01 AU preperihelion) and 1997 September 25.7 (R h = 2.83 AU post-perihelion) using high-resolution infrared spectroscopy. Production rates and rotational temperatures were measured, and the derived heliocentric dependence for ethane production was Q = (5.52 ± 0.20) × 10 28 [R (-2.43 ± 0.13) h ] molecules s -1 . The spatial distribution of C 2 H 6 molecules in the coma was consistent with all ethane being released directly from the nucleus, although the possibility that a small fraction was released as a distributed source cannot be excluded. When our derived production rates for ethane, water, and acetylene (C 2 H 2 ) are compared, we obtain an average relative abundance of C 2 H 6 /H 2 O = (6.23 ± 0.42) × 10 -3 , and C 2 H 6 /C 2 H 2 = 2.4 ± 0.7. The high ethane abundance relative to acetylene in Hale-Bopp suggests its ices were altered by radiation processing and/or hydrogenatom addition reactions on the surfaces of ice-mantled grains in the natal cloud. These results are not consistent with ices in Hale-Bopp originating in a thermally or chemically equilibrated region of the solar nebula.