Solubility of Rock in Steam Atmospheres of Planets

Bruce Fegley Jr, Nathan S. Jacobson, K.B. Williams, J.M.C. Plane, L. Schaefer, Katharina Lodders
(Submitted on 1 Feb 2016)

Extensive experimental studies show all major rocky elements (Si, Mg, Fe, Ni, Ca, Al, Na, K) dissolve in steam to a greater or lesser extent. We use these results to compute chemical equilibrium abundances of rocky element-bearing gases in steam atmospheres equilibrated with silicate magma oceans. Rocky elements partition into steam atmospheres as volatile hydroxide gases and via reaction with HF or HCl as volatile halide gases in much larger amounts than expected from their vapor pressures over volatile-free solid or molten rock at the same temperature. We compute the extent of fractional vaporization by defining gas to magma partition coefficients and show Earth’s sub-solar Si to Mg bulk elemental ratio may be due to loss of a primordial steam atmosphere. We conclude hot rocky exoplanets that are undergoing or have undergone escape of steam atmospheres may experience fractional vaporization and loss of Si, Mg, Fe, Ni, Ca, Al, Na, and K. This loss may modify their bulk composition, density, heat balance, and internal structure.

Comments: 68 pages text and references, 6 tables, 30 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1602.00658 [astro-ph.EP] (or arXiv:1602.00658v1 [astro-ph.EP] for this version)
Submission history
From: Bruce Fegley Jr
[v1] Mon, 1 Feb 2016 20:10:23 GMT (5037kb)
http://arxiv.org/abs/1602.00658