Hydrogen Partitioning in Rocky Planet Cores

Keavin Moore ( Université McGill )

During rocky planet formation, hydrogen partitions between the metallic iron core and silicate magma ocean, governed by the bulk planetary hydrogen budget. Previous studies determined that the vast majority of a planet's hydrogen will partition in the core, with only a small amount remaining dissolved in the magma ocean. This has important consequences for planetary water: there will be less water in the magma ocean to degas an atmosphere, as most of the hydrogen bonds with metal alloy, and this could lead to smaller surface water inventories. We use parameterized equations of mass balance and chemical partitioning to determine the partitioning of hydrogen, and water, between core and magma ocean. We find that a higher bulk planetary water budget does not equally increase the hydrogen in the core, with a crossover from core-dominated to magma-ocean-dominated around 7 Earth Oceans.