Extended Data Fig. 3: Predicted chemical composition of a K2-18 b-like atmosphere from radiative-convective-photochemical and kinetics models.
From: Challenges in the detection of gases in exoplanet atmospheres
A Average volume mixing ratios of gases with abundances exceeding 1 ppm in the 1 mbar-1 μbar region, computed using two independent photochemical kinetics models, Photochem (blue) and Vulcan (red) for an atmosphere with metallicity [M/H] = +2.25 and C/O = 0.8. Only species with infrared-active bands are shown. B Vertical abundance profiles from the 1D radiative-convective-photochemical equilibrium (1D-RCPE) grid for the same composition ([M/H] = 2.25, C/O = 0.8) assuming full heat redistribution. Several hydrocarbons and sulfur-bearing products are present at non-negligible abundances in the observable atmosphere. These species arise from coupled thermochemical, photochemical, and vertical-mixing processes within the modeled atmosphere.
