Seasonal density variations in the Martian thermosphere from observations of UV dayglow by MAVEN/IUVS

Our simulations demonstrate that the peak altitudes of the CO2+ UVD, the Cameron bands and the OI 297.2 nm emissions are good proxies of the amount of CO2 above the emission peaks. In particular, the peak altitudes ZM of the UVD, Cameron and 297.2 nm emissions are directly controlled by the slant CO2 column density overlying the emission peaks. The characteristics of the OI 130 and 135 nm profiles depend on both the O and the CO2 distribution [3]. We take advantage of this feature, combined with the unprecedented quality and coverage of the IUVS limb observations, to map the variations of these emissions observed during the 4 years of the MAVEN mission. In particular, we present the parallel seasonal variations of ZM as a function of latitude and local time of the different emissions. An example for the Cameron and UVD emissions is shown in Fig. 3. We demonstrate that the changes of altitude ZM of different isobar levels co-vary and result from both seasonal surface-atmosphere exchanges and atmospheric dust load following global dust storms. In general, the MCD CO2 density requires only minor scaling to match the observations.