The carbon chemistry of meteorites: Relationships to comets

The carbonaceous meteorites exhibiting alteration by liquid water bear a strong relationship to comets. Not only is their elemental composition closer to solar in relative abundances than other meteorites, they are water rich; and they contain isotopic compositions among refractory and volatile elements indicative of presolar components. Some of these isotopic anomalies occur in organic compounds and carbonaceous grains signifying the presence of discrete and identifiable carbon components derived from interstellar and circumstellar matter. Insofar as comets and meteorites are ultimately formed from interstellar gas and dust, and comets have been subjected to considerably less aqueous and thermal evolution than carbonaceous meteorites, the interstellar imprint should be much stronger and better preserved in comets.