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The relative influence of H 2 O and CO 2 on the primitive surface conditions and evolution of rocky planets
Author(s) -
Salvador A.,
Massol H.,
Davaille A.,
Marcq E.,
Sarda P.,
Chassefière E.
Publication year - 2017
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1002/2017je005286
Subject(s) - atmosphere (unit) , convection , flux (metallurgy) , condensation , solar system , latent heat , ice albedo feedback , atmospheric sciences , planet , albedo (alchemy) , venus , astrobiology , physics , chemistry , thermodynamics , astrophysics , meteorology , organic chemistry , sea ice , art , cryosphere , drift ice , performance art , art history
How the volatile content influences the primordial surface conditions of terrestrial planets and, thus, their future geodynamic evolution is an important question to answer. We simulate the secular convective cooling of a 1‐D magma ocean (MO) in interaction with its outgassed atmosphere. The heat transfer in the atmosphere is computed either using the grey approximation or using a k ‐correlated method. We vary the initial CO 2 and H 2 O contents (respectively from 0.1 × 10 −2 to 14 × 10 −2 wt % and from 0.03 to 1.4 times the Earth Ocean current mass) and the solar distance—from 0.63 to 1.30 AU. A first rapid cooling stage, where efficient MO cooling and degassing take place, producing the atmosphere, is followed by a second quasi steady state where the heat flux balance is dominated by the solar flux. The end of the rapid cooling stage (ERCS) is reached when the mantle heat flux becomes negligible compared to the absorbed solar flux. The resulting surface conditions at ERCS, including water ocean's formation, strongly depend both on the initial volatile content and solar distance D . For D > D C , the “critical distance,” the volatile content controls water condensation and a new scaling law is derived for the water condensation limit. Although today's Venus is located beyond D C due to its high albedo, its high CO 2 /H 2 O ratio prevents any water ocean formation. Depending on the formation time of its cloud cover and resulting albedo, only 0.3 Earth ocean mass might be sufficient to form a water ocean on early Venus.