Coupled evolution of Earth's H2-rich proto-atmosphere and oxidized magma ocean: Efficient H2O production through dissolved H2 transport and atmospheric buffering of the magma ocean redox state
Abstract
Giant impacts during Earth's final accretion likely generated global magma oceans, where the disproportionation of Fe^2+ at lower-mantle pressures and segregation of the resulting metallic iron into the core could have oxidized the magma ocean. Earth may nevertheless have had an H2-rich proto-atmosphere in chemical disequilibrium with the magma ocean, but the chemical coupling between this atmosphere and an oxidized magma ocean remains poorly constrained. Here we develop a coupled atmosphere-interior evolution model that includes diffusive transport in the boundary layer between the magma ocean and atmosphere, redox reactions in the melt, partitioning of oxide components and H2O among coexisting phases, and planetary cooling through a proto-atmosphere, with metallic iron produced by Fe^2+ disproportionation removed into the core as it forms. Atmospheric H2 transport into the magma ocean and subsequent H2O production become more efficient with increasingly frequent boundary layer renewal driven by buoyant overturn of dense melt cooled at the surface, allowing the atmosphere and magma ocean to chemically equilibrate within ~10^4 yr when the magma ocean is sufficiently deep and hot to extend into the lower mantle. Redox exchange with the atmosphere buffers the solidification-driven redox evolution of the magma ocean, preventing extreme oxidation or reduction of the coupled system. These results suggest that the coupled evolution could have contributed to early Earth's water inventory while maintaining a reducing H2-rich atmosphere.
Versions
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BibTeX
@misc{yoshida2026coupled,
title = {{Coupled evolution of Earth's H2-rich proto-atmosphere and oxidized magma ocean: Efficient H2O production through dissolved H2 transport and atmospheric buffering of the magma ocean redox state}},
author = {Tatsuya Yoshida and Kirara Arima and Naoki Terada and Takeshi Kuroda and Kiyoshi Kuramoto},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.38503},
eprint = {2610.38503},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.38503},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Coupled evolution of Earth's H2-rich proto-atmosphere and oxidized magma ocean: Efficient H2O production through dissolved H2 transport and atmospheric buffering of the magma ocean redox state
AU - Tatsuya Yoshida
AU - Kirara Arima
AU - Naoki Terada
AU - Takeshi Kuroda
AU - Kiyoshi Kuramoto
PY - 2026
DA - 2026/10/28
PB - arXiv
DO - 10.48550/arxiv.2610.38503
UR - https://arxiv.org/abs/2610.38503
AB - Giant impacts during Earth's final accretion likely generated global magma oceans, where the disproportionation of Fe^2+ at lower-mantle pressures and segregation of the resulting metallic iron into the core could have oxidized the magma ocean. Earth may nevertheless have had an H2-rich proto-atmosphere in chemical disequilibrium with the magma ocean, but the chemical coupling between this atmosphere and an oxidized magma ocean remains poorly constrained. Here we develop a coupled atmosphere-interior evolution model that includes diffusive transport in the boundary layer between the magma ocean and atmosphere, redox reactions in the melt, partitioning of oxide components and H2O among coexisting phases, and planetary cooling through a proto-atmosphere, with metallic iron produced by Fe^2+ disproportionation removed into the core as it forms. Atmospheric H2 transport into the magma ocean and subsequent H2O production become more efficient with increasingly frequent boundary layer renewal driven by buoyant overturn of dense melt cooled at the surface, allowing the atmosphere and magma ocean to chemically equilibrate within ~10^4 yr when the magma ocean is sufficiently deep and hot to extend into the lower mantle. Redox exchange with the atmosphere buffers the solidification-driven redox evolution of the magma ocean, preventing extreme oxidation or reduction of the coupled system. These results suggest that the coupled evolution could have contributed to early Earth's water inventory while maintaining a reducing H2-rich atmosphere.
ER -