Hakim, Kaustubh ; Bower, Dan J. ; Sossi, Paolo ; Seidler, Fabian

Talk presented at Geologica Belgica, Liege, Belgium on 2024-09-12

Abstract: Atmospheres of hot sub-Neptunes (equilibrium temperatures > 1000 K) are being characterised by the James Webb Space Telescope (JWST). Recent modelling efforts suggest that the magma-atmosphere coupling of hot sub-Neptunes strongly impacts their atmospheric chemistry, enriching the atmosphere in refractory element-bearing gases, e.g., SiO, SiH4. To determine atmospheric chemistry, we implement a new state-of-the-art code, atmodeller, that models an equilibrium chemistry reaction network. Based on the calculations for atmosphere chemistry in the Si-O-H system with mass conservation for H between the atmosphere and the interior, we can classify sub-Neptune populations into steam worlds, hydrogen worlds, and silicon worlds. We quantify the strong impact of including non-ideal gas behaviour and gas solubility in magma on these populations. These populations should exhibit distinct atmospheric signatures that are detectable with JWST transmission and emission spectroscopy.

Funding: FED-tWIN/STELLA/Prf-2021-022