On the Efficacy of Ocean Formation with a Primordial Hydrogen Atmosphere

TL;DR

This study models Earth's early atmosphere and magma ocean to evaluate if primordial hydrogen could have led to water formation, concluding it is unlikely due to rapid outgassing and stable boundary layers preventing oxidation.

Contribution

The paper presents a comprehensive atmosphere-magma ocean model demonstrating that hydrogen-driven water formation on early Earth is improbable due to physical and chemical constraints.

Findings

Water formed would quickly outgas from the atmosphere.

Oxidation reactions produce metallic iron that sinks, stabilizing the boundary layer.

Hydrogen dissolution likely did not significantly contribute to Earth's oceans.

Abstract

It has been suggested that Earth's present water budget formed from oxidation reactions between its initial hydrogen-rich primordial atmosphere and its magma ocean. Here we examine this hypothesis by building a comprehensive atmosphere-magma ocean model. We find that water formation is unlikely for two reasons. First, any water formed from oxidation reactions in the magma ocean would quickly outgass because of the water-poor atmosphere above. Second, the top boundary layer of the magma ocean becomes stable against convection because the oxidation reactions produce metallic iron, which sinks to the core of a growing Earth. This iron loss makes the top boundary layer significantly more buoyant than the rest of the magma, thus becoming stable against mixing. Our results suggest that hydrogen dissolution is unlikely to play a major role in the formation of Earth's oceans.