Clouds on lava planets and where to find them

Giang Nguyen ( Université McGill )

With dayside temperatures hot enough to sustain a dayside magma ocean that guarantees the presence of an outgassed atmosphere, lava planets are the best targets to study the atmosphere of a rocky world. Since the entire atmosphere collapses near the day-night terminator, condensation must be occurring, but the impact of clouds on radiative transfer, dynamics, and observables has not yet been studied. We therefore simulate cloud formation in a hydrodynamical model to determine which lava planets should be most affected by clouds. We find that despite the scattering of visible light from clouds, heat advection in the atmosphere is large enough to compensate for the cooling effect of clouds. On the other hand, surface temperatures are significantly affected and can drop 100-200 K under a cloudy sky. We find that among our targets, HD213885b and HD20329b are most affected by cloud formation and there is a divergence of spectral features between cloudless and cloudy conditions; the precision required to make such an inference is at the limit of current instruments.