Comparing Organics in Comets and in Dense Molecular Clouds

Details Comparing Organics in Comets and in Dense Molecular Clouds Comparing Organics in Comets and in Dense Molecular Clouds

Sep 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009dps....41.2308k&link_type=abstract

American Astronomical Society, DPS meeting #41, #23.08

Biology

Scientific paper

During the early stages of our Solar System, the Earth was frequently bombarded by interplanetary bodies rich in volatiles, such as water and organic material. Tracing the origin and chemical evolution of organic molecules is a fundamental goal of astrobiology. Understanding the chemical evolution of organic molecules requires a detailed accounting of the processing which material undergoes as it evolves from cold molecular clouds, to star-forming cores, to planet-forming disks. The journey likely begins in interstellar molecular clouds, where many simple molecules can be formed via gas-phase reactions. Within dense cold clouds, many molecules freeze-out onto the surfaces of dust grains, and subsequent reactions on the grain surfaces lead to the formation of more complex molecules. When molecular clouds collapse to form protostars, icy grain mantles are subjected to heating and irradiation, which trigger further reactions and changes in composition. In addition, some of the species sublimate and participate in a rich gas-phase chemistry to form more complex molecules. Some of this material is incorporated into planet forming disks. Comets are thought to contain a primordial record of the Solar System. We present here a comparison of abundances of various organic molecules seen toward quiescent molecular clouds, young stellar objects, and comets. We find that the abundances of simple organics vary at the different stages and indicate that comets do not contain a record of the original molecular cloud. Rather, the chemical diversity changes with the various stages of star formation (including planet formation). In an effort to quantify changes in the abundance of organics in water ice with processing, we will also include results from our recent experiments on the thermal evolution of water ice containing organics such as acetylene.

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