Speaker: Eva Zlimen
Affiliation: EPSS, UCLA
Date: Wednesday, May 20, 2026
Time: 12:00 PM
Abstract
Giant impacts are the last major stage in the formation of terrestrial planets. They also are believed to play a major role in the assembly, long-term orbital stability, and resonant structure of exoplanetary systems. Both the mechanical shock and thermal heating of a giant impact can cause atmospheric mass loss. Previous works have shown that for planets with hydrogen-dominated atmospheres, the post-impact thermal heating acts as the dominant mass loss mechanism by inflating the planetary envelope and driving a Parker wind. However, past studies have considered the atmosphere and interior of these planets as discrete, non-chemically-interacting layers. We revisit this idea through the lens of a coupled atmosphere-interior system, allowing for chemical interactions between the core and envelope as the planet experiences heating and subsequent cooling after a giant impact. Considering a miscible interior affects the mean molecular weight of the envelope, allows hydrogen to mix into the core, and modifies the compositional gradients in the planet, thus altering the atmospheric mass loss. We present new results for the atmospheric loss due to giant impacts and discuss their implications for the formation and composition of super-Earths, sub-Neptunes and the radius valley.