Comparison between synthetic spectra and the VIMS spectra. a) In the 1−2 μm range for the selected altitudes of 59, 115, 177, 217, and 315 km. Wavelength intervals in which the model fits are not satisfactory are shown by dashed lines; they correspond to the centers of the Δν = 3, 4, and 5 bands of CH₄ near 1.7, 1.4, and 1.2 μm. b) In the 3.8−5 μm range at the selected altitudes of 59, 115, 177, 217, and 315 km. The synthetic spectra include the influence of CH₄, CH₃D, C₂H₆, CO₂, CO, and haze absorption and scattering. The  ± 2σ error bars for the 1−1.6, 1.8−2, 3.8−4.8, and 4.8−5 μm intervals of the VIMS spectra are adopted from Bellucci et al. (2009).