Effect of mantle oxidation state and escape upon the evolution of Earth's magma ocean atmosphere

The magma ocean is a critical phase determining how Earth's atmosphere developed into habitability. However there are major uncertainties in the role of key processes such as outgassing from the planetary interior and escape to space which determine subsequent atmospheric evolution.  We investigate the impact of outgassing of species and escape of H₂ for different mantle redox states upon the composition and evolution of the atmosphere for the magma ocean period. We include an important new atmosphere-interior coupling namely the redox evolution of the mantle which strongly affects the outgassing of species. We simulate volatile outgassing and chemical speciation at the surface for various redox states of the mantle by employing a C-H-O based chemical speciation model combined with an interior outgassing model.
We then apply a Line-By-Line radiative transfer model (GARLIC) to study the remote appearance of the planet in terms of the thermal infrared emission and transmission. Finally, we use a diffusion-limited and energy-driven  escape model for calculating the loss of H₂ from the atmosphere. We obtain that the outgoing longwave radiation and effective height of the atmosphere are potentially influenced by the redox state of the mantle and the volatile outgassing from the magma ocean. An atmosphere above a reduced mantle consisting of light H₂ emits larger outgoing radiation to space and has a larger effective height compared with heavier, oxidized atmospheres consisting of H₂O and CO₂ lying above an oxidized mantle. We simulate responses in the nature and composition of the atmosphere over the magma ocean period. Results also suggest that outgassing rates of H₂ can be a factor of x10 larger than those of diffusive H₂ escape rate during this period. We evaluate the mass-loss timescale of H₂ via escape of the primary outgassed H₂ atmosphere to be within few tens of Myr. Our work presents useful input to guide future studies such as those discussing exoplanetary interior composition and its possible links with atmospheric composition that might be estimated from observed infrared spectra (via retrieval) by future planned missions such as ELT, ARIEL and JWST etc.