Atmosphere Origins for Exoplanet Sub-Neptunes

Planets with 2 R⊕ < R < 3 R⊕ and orbital period 103 km thick outgassed atmospheres have high mean molecular weight. The hypothesis of magma-atmosphere equilibration links observables such as atmosphere H2O/H2 ratio to magma FeO content and planet formation processes. Our model's accuracy is limited by the lack of experiments (lab and/or numerical) that are specific to sub-Neptunes; we advocate for such experiments.