FIG. 3.

These nine panels each show model-predicted vertical profiles of the mixing ratios of the greenhouse gases in our climate and line-by-line radiative transfer models. Panels on the left are for planets orbiting stars with greater UV radiation, and panels on the bottom are for planets with higher biological S_org production. H₂O and CO₂ concentrations are identical in all model runs, while CH₄ concentrations vary only modestly between simulations. Note the increase in C₂H₆ concentrations on planets with higher S_org fluxes or lower UV radiation, or both. Color images available online at www.liebertonline.com/ast