Puffy Venuses and their others: the puzzles of irradiated, underdense rocky worlds

An emerging population of irradiated, low-mass exoplanets falls close to rocky bulk densities but are underdense relative to Earth-like composition. In this talk, I will first discuss my previous work, where Prof. Diana Valencia and I proposed puffy Venuses, magma ocean worlds with thick carbon-rich atmospheres, as a potential explanation. To this end, we constructed a coupled magma-ocean atmosphere model that accounted for carbon and hydrogen partitioning between the atmosphere and molten mantle, as well as the C-H-O thermochemistry in a dual-gray radiative-convective atmosphere. We demonstrated that moderate, chondritic C abundance can generate observable underdensity in puffy Venuses, and highlighted exoplanet candidates for this interpretation. I will then discuss recent theoretical and observational works in relation to puffy Venuses. Finally, I will present my ongoing work with Prof. Laura Schaefer on C precipitation in rocky planets. C precipitation, in both the atmosphere and the interior, can facilitate the long-term survival of an outgassed atmosphere by enhancing their C storage capacity. This is because C precipitation can both limit the atmosphere’s mass and form a mantle C reservoir independent from dissolved atmospheric species. We adapt the puffy Venus atmosphere model to probe the irradiation and redox conditions that lead to C precipitation-limited atmospheres, and their observational consequences. We also discuss the phases and distribution of atomic C in the primordial magma oceans of C-rich super-Earths by calculating their buoyancy in molten MgSiO3 across wide P-T ranges. 

Attend in person or watch online (see weblink). Room 350/372

Speaker: Bo Peng, Stanford University