February 4
Sub-Neptunes from top to bottom: how interior-atmosphere coupling affect small exoplanets
Dr. William Misener
Carnegie Postdoctoral Fellow at the Earth and Planets Laboratory
Abstract: Sub-Neptunes and super-Earths are the most abundant class of planet yet discovered, but their formation, evolution, and even bulk properties remain mysterious. Many processes, from initial accretion to atmosphere-interior interactions to atmospheric escape, are thought to play a major role in shaping the planets we observe today. A key result thus far is that treating these processes together, that is, considering sub-Neptunes as complete, coupled systems from their upper atmospheres to deep interiors, is vital for understanding their evolution, structure, and composition. In this talk, I will present my recent work on how feedbacks between sub-Neptune interiors and atmospheres changes our understanding of these ubiquitous planets. First, I will present coupled structure-chemistry models of sub-Neptune envelopes to show that allowing silicates to evaporate from an underlying magma ocean into a hydrogen-rich atmosphere leads to novel physical and chemical interactions, leading to changes in the atmospheric structure and producing abundant water and reduced magma species potentially observable with JWST. Second, I will use hydrodynamic models to unify core-powered and photo-evaporative escape, two competing mechanisms proposed to explain small planet evolution, into a unified framework that can explain the exoplanet population and ongoing ground- and space-based observations of atmospheric escape. These results underscore the need to model small exoplanets holistically, accounting for interactions between their interiors and atmospheres.
Host: Ankita Bera