SMuK 2021 – scientific programme

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EP: Fachverband Extraterrestrische Physik

EP 5: Exoplanets and Astrobiology I

EP 5.4: Talk

Wednesday, September 1, 2021, 17:30–17:45, H9

Redox hysteresis of super-Earth exoplanets from magma ocean circulation — •Tim Lichtenberg — Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, United Kingdom

From an astronomical perspective, planets that formed under similar conditions should exhibit comparable compositional trends, such as volatile inventory, which can be compared to hypothetical M-R relations. However, internal redox reactions may irreversibly alter the mantle composition and volatile inventory of terrestrial and super-Earth exoplanets, which can affect their outgassed atmospheres and decouple the initial accreted composition from long-term climate. The global efficacy of these mechanisms hinges on the transfer of reduced iron from the molten silicate mantle to the metal core. Using scaling analysis I demonstrate that turbulent diffusion in the internal magma oceans of sub-Neptune exoplanets can kinetically entrain liquid iron droplets and quench core formation. This suggests that the chemical equilibration between core, mantle, and atmosphere may be energetically limited by convective overturn in the magma flow. Hence, molten super-Earths possibly retain a compositional memory of their accretion path. Redox control by magma ocean circulation positively correlates with planetary heat flow, internal gravity, and planet size. The presence and speciation of remanent atmospheres, surface mineralogy, and core-mass fraction of atmosphere-stripped exoplanets may thus constrain magma ocean dynamics and can be probed by upcoming observational facilities.