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[31.03] Spectroscopic Signatures of the Accretion of Earth-like Exoplanets

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

We used thermochemical equilibrium calculations to model the chemistry of silicate vapor and steam-rich atmospheres formed during accretion of Earth-like exoplanets. Accretion models that show temperatures of several thousand degrees during accretion of the Earth motivated this work. These models also predict the formation of a steam-rich atmosphere during the later stages of Earth's accretion. Our results show that silicon monoxide (SiO) gas is the major species in silicate vapor atmospheres for T > 3080 K, and monatomic Na gas is the major species for T < 3080 K (see figure). During later, cooler stages of accretion (1500 K), the major gases (abundances >1%) in a steam-rich atmosphere are H₂O, H₂, CO₂, CO, H₂S, and N₂. CO converts to CH₄ as the steam atmosphere cools. The dependence of gas chemistry on T and P over wide ranges was computed. The NASA Astrobiology Institute and Origins Program supported this work.

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