Retrieval of Martian Atmospheric CO Vertical Profiles From NOMAD Observations During the First Year of TGO Operations

We present CO density profiles up to about 100 km in the Martian atmosphere obtained for first time from retrievals of solar occultation measurements by Nadir and Occultation Mars Discovery (NOMAD) onboard ExoMars Trace Gas Orbiter (TGO). is an important trace gas on Mars, as it controlled CO2 photolysis, chemical reaction with OH radicals, global dynamics. However, vertical have been elusive until arrival TGO. show how NOMAD variations describe very well general circulation. observe a depletion upper troposphere mesosphere during peak period, LS = 190°–200°, more pronounced over northern latitudes, confirming similar result recently reported Atmospheric Chemistry Suite lower around 20 km, at least high latitudes S. hemisphere, mixing ratios increase 1,500 ppmv GDS (Global Dust Storm) onset. This might be related downwelling branch Hadley A subsequent tropospheric observed decay phase 210°–250° when dust loading still high. could associated reduction amount radicals due lack insolation. Once over, steadily decreases globally southern summer season. couple distinct patterns Summer solstice equinox circulation are discussed.