Martian thermospheric temperatures retrieved from CO2 + SPICAM dayglow measurements

A large dataset of dayside grazing limb CO2+ observations performed by the SPICAM (Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars) instrument on board Mars Express is analyzed to retrieve Martian thermospheric temperature, as well as its variation with solar activity, season and latitude. The method permits to retrieve the temperature from the scale height of the CO2+ emission. We also present puzzling features such as limb profiles exhibiting multiple peaks and their characteristics. We furthermore study the behavior of the main emission peak of the CO2+ vertical emission profiles. The CO2+ emission at 289 nm arises from the relaxation of the CO2+* molecule in the B2Σ+ state to the X2Π state. CO2+* molecules are mainly produced in the Martian dayside through photoionisation and photoelectron impact. The CO2+ emission exhibits features that constrain the temperature and density vertical profiles of CO2. Comparisons of retrieved temperatures are made with corresponding simulations from the coupled MGCM-MTGCM. We also use a Monte-Carlo code to model the observed intensity limb profiles.