Atmospheric Composition and Organic Production: the Early Cometary Bombardment

C. P. McKay (NASA Ames), W. J. Borucki (NASA Ames)

Recent paleontological evidence indicates that life was present on Earth as early as 3.9 Gyr ago. In this case life arose on this planet during the late stages of accretion. It is likely that the main influx of volatile material during this time was due to cometary infall. We use the known composition of Comet Halley to model the probable composition of an atmosphere dominated by cometary volatiles. We also present experimental results which show that shock processes in an atmosphere of cometary volatiles are capable of producing organic compounds that could have been relevant to the emergence of life.