Speaker: Prof. Ray Pierrehumbert , Halley Professor of Physics, University of Oxford
Abstract: In this lecture, I will highlight some examples of the interplay between planetary envelopes and planetary interiors, focusing on lava planets, "hot rocks" (rocky planets too hot to support surface liquid water but not hot enough to have molten surfaces), the deep carbon cycle on habitable rocky worlds, and sub-Neptunes. Recent JWST data driving these inquiries will be surveyed. The general programme is to determine the extent to which astronomical observations -- which probe only the outer skin of a planet's volatile envelope (if present)-- together with mass, radius and age data can constrain the composition and structure of the interior, which cannot be directly observed. sub-Neptunes present an especially interesting case, because many currently accessible targets have a predominantly rocky composition (by mass), surrounded by a lower molecular weight envelope which interacts physically and chemically with a permanent magma ocean at the silicate/envelope interface. For sub-Neptunes with a sufficiently massive envelope, the interface with the silicate mantle can be hot enough to drive the silicate itself supercritical, blurring the distinction between mantle and envelope. Lack of experimental data on equations of state, geochemical reaction constants and opacities currently constitutes a serious impediment to progress in modelling sub-Neptune thermochemical structure and evolution.