Top panel: N₂, CH₄, and H densities we supply as inputs to the 1D model. Above the exobase, the H densities follow a Chamberlain model profile (J. W. Chamberlain 1963). The black dashed line marks the altitude at which the vertical optical depth from H scattering at Lyα line center reaches unity. The gray dashed line marks the altitude at which the vertical optical depth from CH₄ absorption at Lyα line center reaches unity. Bottom panel: 1D model temperature profile.