Prof. Hilke Schlichting (UC Los Angeles)

Super-Earths and sub-Neptunes are the most abundant exoplanets discovered in our galaxy to date. However, much of their nature and origin remains shrouded in mystery. Generally speaking, super-Earths and sub-Neptunes are thought to have formed with primordial hydrogen-dominated envelopes and as one population. However, most super-Earths lost their primordial atmospheres via thermally driven winds. In my talk, I will present global chemical equilibrium models of super-Earths and sub-Neptunes. I will show that magna-ocean atmosphere interactions expected in sub-Neptunes exoplanets lead to signatures in their transmission spectra that are readily observable with JWST. In addition, hydrogen is efficiently sequestered into the interior, oxidizing iron and endogenously producing ∼0.5%–1.0% water by mass. One of the main effects of efficient sequestration of hydrogen into the interior is the formation of under-dense bulk interiors compared to Earth’s. I will conclude by discussing possible parallels between Earth’s formation and that of super-Earths, shedding new light Earth’s primary water reservoir.