Extended Data Fig. 7: Grid exploration of the miscible envelope sub-Neptune scenario for LP791-18c.
From: Diversity in the haziness and chemistry of temperate sub-Neptunes
a. Carbon dioxide-to-methane abundance ratio at 10 mbar for a grid of convective-radiative SCARLET models of LP 791-18 c for which vertical mixing was modelled using the VULCAN framework with a Kzz of 104 cm2/s. The colorbar is cut at log10CO2/CH4 values of +2.5 and − 2.5 in order to help visualize the transition from methane dominated to carbon dioxide dominated regimes. The 2σ upper bound on the carbon dioxide-to-methane abundance ratio derived from the free chemistry retrieval is shown as the black line and arrows. b. Mixing ratios of a sample model of the grid shown on the left for the case of 0.0 Bond albedo and 300 × solar metallicity. The temperature-pressure profile is shown as the black dashed line with the corresponding temperature axis at the top. At the temperature regime of LP 791-18 c, CH4 strongly dominates over CO2 unless the metallicity is increased above 500 × solar.
