PSI SEMINAR SERIES: 22 September 2004, 3:30pm
"Comet Cosmochemistry"
The chemical composition of cometary material was literally frozen into these small kilometer-sized objects 4.6 Gyr ago, preserving information about the chemical state of the proto-solar cloud. Thanks to spacecraft probes and ground-based observations of recent bright comets, our understanding of the chemical compositions of comets has drastically improved during the past few years. Key isotopic and molecular abundances will be reviewed and discussed. Carbon isotope abundances in several comets are consistent with the solar system value, yet different from the local interstellar value, indicative of significant galactic 13C-enrichment over the past 4.6 Gyr. Comet D/H and 15N/14N ratios indicate preserved interstellar material in several comets. However, the abundance of N2 in comets remains elusive and somewhat controversial. The "N2 problem" will be reviewed in the context of comets, other icy solar system bodies and molecular clouds.
