Deep volatile reservoirs in super-Earths and sub-Neptunes

There is a lot of enthusiasm in the exoplanet community for the detection and characterization of super-Earth and sub-Neptunes. These planets seem most abundant among observable planets, and yet we know little about their interiors. Indirect evidence implies that sub-Neptunes have thick H/He envelopes on top of massive magma oceans, while super-Earths have lost their H/He envelopes. There is a lack of similar planets in the Solar System and therefore their origin and atmospheric evolution represent an important challenge for our understanding of planets.

Moreover, the majority of current formation and evolution models suffer from simplified assumptions of chemically inert interiors and cold rocky interiors in solid-state, as well as the neglect of volatile-exchange at the rock-atmosphere interface. This prevailing view is shifting: (1) the majority of exoplanets are partly molten, i.e., they host global magma oceans; (2) redox reactions between magma and atmospheric volatiles affect bulk composition; and (3) magma oceans represent huge reservoirs for volatiles. The exoplanet community is just beginning to explore new dimensions of these complexities. I will give an overview of general and personal efforts on this front.