What Comets Tell us About Prebiotic Chemistry in Protoplanetary Disks

Details What Comets Tell us About Prebiotic Chemistry in Protoplanetary Disks What Comets Tell us About Prebiotic Chemistry in Protoplanetary Disks

Dec 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006aas...20912402m&link_type=abstract

2007 AAS/AAPT Joint Meeting, American Astronomical Society Meeting 209, #124.02; Bulletin of the American Astronomical Society,

Biology

Scientific paper

Sophisticated ground-based instrumentation on large telescopes, along with new space mission results are revealing new information about comets which provides insight into the chemistry of the proto-planetary disk out of which they formed. This new chemical information is changing our paradigm of solar system formation. This talk will review results from recent ground-based observations as well as results from the NASA Deep Impact mission. It has long been expected that comet surfaces must be thermally processed, and that inferring primordial chemical composition from the observed escaped gas is difficult because of chemistry which may occur in the gas cloud after leaving the nucleus. The Deep Impact mission provided clear evidence for thermal processing of the surface layers. There was a large increase in the organic fraction seen in the ejecta post-impact, and in the relative abundances of some organic species. Accepted comet formation models have postulated that the comet is built up of discrete cometesimals which may exhibit chemical heterogeneity as a result of radial migration in the disk. Images from the Deep Impact mission, however, showed layered structure on the comet which may have implications for different formation scenarios. Deep Impact observers saw evidence for crystalline silicates, similar to those seen in other comets, requiring a high-temperature crystallization mechanism in the disk. In addition to summarizing the current state of comet observations as they constrain our understanding of protoplanetary disk chemistry, we will discuss the types of observations that can be made as new facilities come on line and the Rosetta mission returns information, in particular to explore D/H chemistry.
This material is based upon work supported by the National Aeronautics and Space Administration through the NASA Astrobiology Institute under Cooperative Agreement No. NNA04CC08A issued through the Office of Space Science.

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