Kavli Affiliate: Laura Schaefer
| First 5 Authors: Frances E. Rigby, Lorenzo Pica-Ciamarra, Måns Holmberg, Nikku Madhusudhan, Savvas Constantinou
| Summary:
The recent JWST detections of carbon-bearing molecules in a habitable-zone
sub-Neptune have opened a new era in the study of low-mass exoplanets. The
sub-Neptune regime spans a wide diversity of planetary interiors and
atmospheres not witnessed in the solar system, including mini-Neptunes,
super-Earths, and water worlds. Recent works have investigated the possibility
of gas dwarfs, with rocky interiors and thick H$_2$-rich atmospheres, to
explain aspects of the sub-Neptune population, including the radius valley.
Interactions between the H$_2$-rich envelope and a potential magma ocean may
lead to observable atmospheric signatures. We report a coupled
interior-atmosphere modelling framework for gas dwarfs to investigate the
plausibility of magma oceans on such planets and their observable diagnostics.
We find that the surface-atmosphere interactions and atmospheric composition
are sensitive to a wide range of parameters, including the atmospheric and
internal structure, mineral composition, volatile solubility and atmospheric
chemistry. While magma oceans are typically associated with high-temperature
rocky planets, we assess if such conditions may be admissible and observable
for temperate sub-Neptunes. We find that a holistic modelling approach is
required for this purpose and to avoid unphysical model solutions. We find
using our model framework and considering the habitable-zone sub-Neptune K2-18
b as a case study that its observed atmospheric composition is incompatible
with a magma ocean scenario. We identify key atmospheric molecular and
elemental diagnostics, including the abundances of CO$_2$, CO, NH$_3$ and,
potentially, S-bearing species. Our study also underscores the need for
fundamental material properties for accurate modelling of such planets.
| Search Query: ArXiv Query: search_query=au:”Laura Schaefer”&id_list=&start=0&max_results=3