Clouds in Partial Atmospheres of Lava Planets and Where to Find Them

Abstract With dayside temperatures hot enough to sustain a magma ocean and a silicate atmosphere, lava planets are the best targets for studying the atmosphere of a rocky world. In the absence of nightside heating, the entire atmosphere collapses near the day–night terminator, so condensation seems inevitable, but the impact of clouds on radiative transfer, dynamics, and observables has not yet been studied in the nonglobal atmospheric regime. Therefore, we simulate cloud formation and determine which lava planets should be most affected by clouds. We find that despite the scattering of visible light by clouds, heat advection compensates for the cooling effect of clouds in the atmosphere. On the other hand, surface temperatures are significantly affected and can drop by 100–200 K under a cloudy sky. We find that among our targets, HD213885b and HD20329b are most affected by cloud formation: there is a discernible difference between having clouds and not having them, but the precision required to make such an inference is at the limit of current instruments.