Variations of the Martian cold oxygen exosphere derived from the O 130.4 nm line by IUVS/MAVEN
Résumé
The Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has systematically observed the Martian oxygen exosphere for nearly one Martian year now. The OI 130.4 nm resonance scattering line is observed all the time at the dayside providing unprecedented information on the oxygen content of the Martian upper atmosphere. These variations are important to understand the chemistry, dynamics, energetics and escape processes of the Martian upper atmosphere. Using a radiative transfer model, we have estimated the amount of oxygen in the Martian exosphere needed to reproduce the observations of IUVS during the first Martian year of the mission. In this work, we will present the seasonal variations of the exospheric oxygen density derived from this set of observations and discussed these variations in the frame of global models of the Martian upper atmosphere.