Thermal spectral emission for a reducing atmosphere overlying a reduced mantle (IW-4) for scenarios 2.1, 2.2, and 2.3 of Table 5. The legend shows the mole fraction of the outgassed species obtained from the speciation model. Prominent features of absorbing species are seen at wavelengths marked in the figure. Reference blackbody curves for three different surface temperatures are plotted. The insets show the zoomed-in thermal spectra with the most prominent absorption features of CO₂, CO and H₂. The spectra have been binned to a resolution of λ∕Δλ = 1000.