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[29.15] A Reducing Atmosphere From Out-gassing of the Early Earth

L. Schaefer, B. Fegley, Jr. (Planetary Chemistry Laboratory, Department of Earth and Planetary Sciences, Washington University, St. Louis, MO)

Earth's present atmosphere originated from out-gassing of volatile-bearing grains. We calculated the composition of volatiles out-gassed from chondritic planetary bodies. We present results for average CI, CM, CV, H, L, and EH chondrites, which are the building blocks of the Earth. From the oxygen-isotope mixing (OIM) model, we calculated a composition of 70% EH, 21% H, 5% CV, and 4% CI chondritic matter for the early Earth. The major out-gassed volatiles for these starting compositions are CH₄, N₂, NH₃, H₂, and H₂O. The Miller-Urey experiment demonstrated that a reducing atmosphere like this generates amino acids and other organic compounds that are essential for the formation of life. This work is supported by the NASA Astrobiology Program.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.