Partitioning of Atmospheric O2 into High-pressure Ice in Ocean Worlds

Abstract

Abstract Planets with a few percent water by mass may have a high-pressure ice mantle separating the rocky interior from both the ocean and atmosphere. Here we examine whether the partitioning of O2 into high-pressure ice can constrain the atmospheric abundance of O2 produced by water photolysis in the atmosphere. We find that the partition coefficient of dissolved O2 between high-pressure ice and liquid water is about unity. We show that the solubility of O2 in high-pressure water ice yields an upper value for the atmospheric abundance of O2 that depends on the ocean surface temperature. The atmospheric pressure of O2 has a maximum of approximately 3000 bars. The latter drops to a few hundred bars as the surface temperature of the ocean approaches supercritical conditions.