How do magma oceans change sub-Neptune atmospheres? · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title
How do magma oceans change sub-Neptune atmospheres?
Plain
Under a thick hydrogen layer, the rocky surface of a sub-Neptune may be molten, and hydrogen can dissolve into it and react with the rock to make water and other gases. This would change what the planet's atmosphere looks like from outside.
Precise · changed · core
Revision 1: For sub-Neptunes with surface magma oceans at T ~ 2000-4000 K under H2 envelopes of ~ 1-3 percent of the planet mass, determine how H2 dissolution into silicate melt and reactions with the melt (FeO and SiO2 reduction producing H2O, SiO and SiH4) set the envelope composition and its mean molecular weight $\mu$. The answer is predicted $\mu$ and H2O, CO2 and SiO abundances versus equilibrium temperature and envelope mass fraction, testable against JWST spectra.
Revision 2: For sub-Neptunes with surface magma oceans at $T \sim 2000-4000\,\mathrm{K}$ under $\mathrm{H_2}$ envelopes of $\sim 1-3\,\mathrm{percent}$ of the planet mass, determine how $\mathrm{H_2}$ dissolution into silicate melt and reactions with the melt (FeO and $\mathrm{SiO_2}$ reduction producing $\mathrm{H_2O}$, SiO and $\mathrm{SiH_4}$) set the envelope composition and its mean molecular weight $\mu$. The answer is predicted $\mu$ and $\mathrm{H_2O}$, $\mathrm{CO_2}$ and SiO abundances versus equilibrium temperature and envelope mass fraction, testable against JWST spectra.
Settled by
Coupled magma-atmosphere equilibrium and evolution models that predict the dependence of $\mu$ on equilibrium temperature, confirmed by JWST spectra of a sample of sub-Neptunes spanning that temperature range.
Kind
phenomenon
Answer type
mechanism
References
(empty)
Literature status
open
Status note
(empty)
Posed since
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Decisions