Thermal Structure of the Middle and Upper Atmosphere of Mars From ACS/TGO CO ₂ Spectroscopy

Temperature and density in the upper Martian atmosphere, above ∼100 km, are key diagnostic parameters to study processes of species' escape, investigate impact solar activity, model atmospheric circulation, plan spacecraft descent or aerobraking maneuvers. In this paper, we report vertical profiling carbon dioxide (CO2) temperature from Atmospheric Chemistry Suite (ACS) occultations onboard ExoMars Trace Gas Orbiter. A strong CO2 absorption band near 2.7 μm observed by middle infrared spectrometric channel (ACS MIR) allows retrieval thermal structure an unprecedentedly large altitude range, 20 180 km. We present latitudinal seasonal climatology for 1.5 years (MYs), MY 34 end 35. The results show variability distinct layers, such as a mesopause (derived 70 145 km) homopause, changing 90 100 km at aphelion 120–130 perihelion. Some short-term homopause fluctuations also depending on dust activity.