Biology
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p14a..04s&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #P14A-04
Biology
[0343] Atmospheric Composition And Structure / Planetary Atmospheres, [5205] Planetary Sciences: Astrobiology / Formation Of Stars And Planets, [5210] Planetary Sciences: Astrobiology / Planetary Atmospheres, Clouds, And Hazes, [5225] Planetary Sciences: Astrobiology / Early Environment Of Earth
Scientific paper
Atmospheric formation on rocky planets (both in our solar system and in other planetary systems) can be divided into three stages [1]. The first stage is a silicate vapor atmosphere produced during accretion when energy deposition is large enough to melt and partially vaporize rocky material (Fe, silicates, sulfides). One source of large energy comes from giant impacts. The Moon-forming impact exemplifies this stage for the Earth [1,2]. For exoplanets, other sources, such as stellar insolation and tidal heating, may produce sufficient heat to melt and vaporize a rocky planet. For example, stellar insolation is sufficient for the hot, rocky exoplanet CoRoT-7b to have a silicate vapor atmosphere [3]. The second stage of atmosphere formation is the generation of a "steam" atmosphere. This stage also occurs during accretion, when energy deposition is still high, but insufficient to vaporize rocky material. Depending on the redox state of the accreted materials, the "steam" atmosphere may contain varying amounts of water vapor. Enstatite, ordinary, and CV chondritic materials are examples of reduced materials that give an H2O-poor "steam" atmosphere, whereas CI and CM chondritic materials are more oxidized and generate an H2O-rich "steam" atmosphere [4,5]. The third stage of atmosphere formation, which occurs both during and after the accretion of most of the planetary mass, is outgassing of the accreted material. The oxidation state of the planet's silicate material may evolve as planetary processes, such as core formation and differentiation, proceed. As the oxidation state changes from more reducing (e.g., like that of chondritic material) to more oxidizing (e.g., like that of the bulk silicate Earth BSE), atmospheric composition changes similarly. Outgassing of BSE material produces a CO2-rich atmosphere that also contains water vapor and SO2 [6, 7]. In this talk we focus on this third stage atmosphere, which is also relevant for understanding the atmospheres of rocky exoplanets. This work was supported by NSF Astronomy Grant #0707377.
Fegley Bruce Jr.
Lodders Katharina
Schaefer L. K.
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