18 October 2001 CfA Colloquium


Title: A Current View of Organic Volatiles in Comets

Speaker: Michael Mumma

Abstract:

Cometary nuclei are remnants of the early solar system. They contain key information from the time when planets were forming, and even earlier; ome contain material from the natal interstellar cloud. The most easily modified forms of matter-- the ices, low-temperature-refractory organics, and minerals-- bear special significance for understanding processes affecting material during its journey from the natal cloud core through the young planetary system. Comets Hyakutake and Hale-Bopp were the first bright comets to be studied with powerful new astronomical facilities. A wealth of new information on cometary organic composition was obtained from them, including the discovery of symmetric hydrocarbons (methane, ethane, acetylene) by infrared spectroscopy and of six new molecular species at radio wavelengths. Since then, larger telescopes (e.g. Keck) and even more powerful instruments (e.g. NIRSPEC) have become available, driving a revolution in our ability to characterize native ices. The organic composition of six comets from the Oort-cloud reservoir (including the unusual disrupted comet C/2000 S4) will be compared and discussed in the context of heterogeneity in the giant-planets' nebular region. Implications for future studies of Oort-cloud and Jupiter-family comets will be mentioned.

References for students:

"A survey of organic volatiles and dust in comet C/1999 H1 (Lee) with NIRSPEC at the Keck Observatory", M. J. Mumma et al. 2001, ApJ, 546,1183

"Organic composition of C/1999 S4 (Linear): a comet formed near Jupiter?", M. J. Mumma et al. 2001, Science, 292, 1334

"Comets: A link between Interstellar and Nebular chemistry" W. F. Irvine, F. P. Schloerb, J. Crovisier, B. Fegley, and M. J. Mumma, in Protostars and Planets IV, eds. V. Mannings, A. P. Boss, and S. S. Russell, (Univ. of Ariz. Press, Tucson) p. 1159

Lunch with the students will be on Friday, October 19 at 12:00 in A-101.