Probing sub‑Neptune interiors through their atmospheres: The case of K2‑18 b

Sub-Neptune exoplanets are the most common class of planets detected to date. They occupy the transitional regime between rocky planets and gas giants, yet degeneracies in their internal structure leave their compositions poorly constrained. Studying their atmospheres provides avenues for inferring their interiors.

In this talk, I will discuss how atmospheric chemistry and formation pathways shape sub-Neptune atmospheres, and how observed spectra can be used to learn their interior structure and potential habitability. Using the temperate sub-Neptune K2-18 b as a case study, I will highlight several diagnostics that can be generalized to the broader population. I will examine how orbital dynamics and cloud formation modulate observable water signatures, and present an agnostic framework to test chemical consistency in order to distinguish between different interior structures. I will conclude with an outlook on key concepts and directions for future studies.