Retrieval of CO₂ and N₂ in the Martian thermosphere using dayglow observations by IUVS on MAVEN

Abstract : We present direct number density retrievals of carbon dioxide (CO₂) and molecular nitrogen (N₂) for the upper atmosphere of Mars using limb scan observations during October and November 2014 by the Imaging Ultraviolet Spectrograph on board NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. We use retrieved CO₂ densities to derive temperature variability between 170 and 220 km. Analysis of the data shows (1) low-mid latitude northern hemisphere CO₂ densities at 170 km vary by a factor of about 2.5, (2) on average, the N₂/CO₂ increases from 0.042 ± 0.017 at 130 km to 0.12 ± 0.06 at 200 km, and (3) the mean upper atmospheric temperature is 324 ± 22 K for local times near 14:00.