Elements Covers

Posts by Scott A. Sandford

Organic Molecules and Volatiles in Comets

Organic molecules and volatiles (e.g. H2O, CO, CO2) are the major components of comets. The majority of the organic compounds found within comets were produced by ice irradiation in dense molecular clouds and in the protoplanetary disk prior to comet formation. Comets are essentially repositories of protocometary material. As a result, comets do not show the clear trends in chemical and isotopic compositions that would be expected from our understanding of their formation locations. Rather, comets record chemical evolution in the protoplanetary disk and allow us to unveil the formation history of the organics and volatiles.

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Organic Matter in Cosmic Dust

Organics are a significant component of most cosmic dust, as revealed from actual samples of extraterrestrial dust in the Earth’s stratosphere, in Antarctic ice and snow, in near-Earth orbit, and in asteroids and comets. Cosmic dust contains a diverse population of organic materials that owe their origins to a variety of chemical processes occurring in many different environments. The presence of isotopic enrichments of D and 15N suggests that many of these organic materials have an interstellar or protosolar heritage. The study of these samples is of considerable importance because they are the best preserved materials of the early Solar System available.

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