000006833 001__ 6833
000006833 005__ 20240217112353.0
000006833 0247_ $$2DOI$$a10.3847/PSJ/ac5fb1
000006833 037__ $$aSCART-2024-0089
000006833 100__ $$aBower, Dan J. 
000006833 245__ $$aRetention of Water in Terrestrial Magma Oceans and Carbon-rich Early Atmospheres
000006833 260__ $$c2022
000006833 520__ $$aMassive steam and CO2 atmospheres have been proposed for magma ocean outgassing of Earth and terrestrial planets. Yet formation of such atmospheres depends on volatile exchange with the molten interior, governed by volatile solubilities and redox reactions. We determine the evolution of magma ocean–atmosphere systems for a range of oxygen fugacities, C/H ratios, and hydrogen budgets that include redox reactions for hydrogen (H2–H2O), carbon (CO–CO2), methane (CH4), and solubility laws for H2O and CO2. We find that small initial budgets of hydrogen, high C/H ratios, and oxidizing conditions suppress outgassing of hydrogen until the late stage of magma ocean crystallization. Hence, early atmospheres in equilibrium with magma oceans are dominantly carbon-rich, and specifically CO-rich except at the most oxidizing conditions. The high solubility of H2O limits its outgassing to melt fractions below ∼30%, the fraction at which the mantle transitions from vigorous to sluggish convection with melt percolation. Sluggish melt percolation could enable a surface lid to form, trapping water in the interior and thereby maintaining a carbon-rich atmosphere (equilibrium crystallization). Alternatively, efficient crystal settling could maintain a molten surface, promoting a transition to a water-rich atmosphere (fractional crystallization). However, additional processes, including melt trapping and H dissolution in crystallizing minerals, further conspire to limit the extent of H outgassing, even for fractional crystallization. Hence, much of the water delivered to planets during their accretion can be safely harbored in their interiors during the magma ocean stage, particularly at oxidizing conditions.
000006833 594__ $$aNO
000006833 700__ $$aHakim, Kaustubh 
000006833 700__ $$aSossi, Paolo A. 
000006833 700__ $$aSanan, Patrick
000006833 773__ $$c28$$n4$$pPlanetary Science Journal$$v3$$y2022
000006833 8560_ $$fkaustubh.hakim@ksb-orb.be
000006833 85642 $$ahttps://doi.org/10.3847/PSJ/ac5fb1
000006833 8564_ $$s3376049$$uhttp://publi2-as.oma.be/record/6833/files/Bower_2022_Planet._Sci._J._3_93.pdf
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000006833 905__ $$apublished in
000006833 980__ $$aREFERD