Substantial water retained early in Earth's deep mantle.

Abstract

Earth's water was likely acquired early, when our planet was extensively molten because of large to giant impacts. How such early water was retained and distributed within a crystallizing mantle remains unclear. In this study, we investigated partitioning of water between bridgmanite, the first and primary mantle mineral to crystallize, and coexisting melt through systematic high-pressure experiments. Our results demonstrate that partitioning of water into bridgmanite is strongly enhanced by increasing temperature. Thus, appreciable amounts of water may have been retained in the lower mantle after its crystallization. Circulation of such early stored water in Earth's interior could have modulated mantle dynamics and influenced the transition of early Earth to a habitable planet.