Inside out: Volatile partitioning experiments and modelling to constrain the rocky planet interior-atmosphere connection

One of the most characterizable types of rocky exoplanets for the coming decades are magma worlds, those with extensive lava or magma oceans at their surfaces, due to their hot, extended atmospheres. At present, the nature and composition of these planets’ atmospheres are poorly constrained because they are strongly connected to their interiors and are modulated by the solubilities of major gases in the magma. In preparation for near-term observations of these exoplanets, we need to understand how volatile elements partition between the interior and atmosphere for diverse planetary compositions. To fill this gap, we performed new H2 solubility experiments on planetary melt analog materials at high temperatures using a 1-bar H2-CO2 gas-mixing furnace. I will present the findings of our experiments and discuss how they can be incorporated into a new volatile partitioning code, Atmodeller, which computes chemical equilibrium at the surface-atmosphere interface of low-mass planets. Coupling laboratory experiments and numerical models is essential for understanding the interior-atmosphere connection for rocky exoplanets and ensuring that upcoming observations of these worlds are properly interpreted.