Comets as a Source of Prebiotic Organic Molecules for the Early Earth

Abstract

Several mechanisms seem likely to have been delivering exogenous organics to the surface of the Earth, or shock-synthesizing them in impacts. In an early carbon dioxide-rich terrestrial atmosphere, these mechanisms would have quantitatively rivaled or exceeded terrestrial organic synthesis in situ. In an early reducing (methane-rich) atmosphere, the exogenous sources would have been quantitatively unimportant compared to atmospheric production.