A Two Martian Years Survey of Water Ice Clouds on Mars with ACS onboard TGO

Aurélien Stcherbinine (1, 2) , Franck Montmessin (1) , Mathieu Vincendon (3) , Michael J. Wolff (4) , Margaux Vals (1) , Oleg Korablev (5) , Anna Fedorova (5) , Alexander Trokhimovskiy (5) , Gaetan Lacombe (1) , Lucio Baggio (1)

1 PLANETO - LATMOS
2 Department of Astronomy and Planetary Science [Flagstaff]
3 IAS - Institut d'astrophysique spatiale
4 SSI - Space Science Institute [Boulder]
5 IKI - Space Research Institute of the Russian Academy of Sciences

The middle infrared (MIR) channel of the Atmospheric Chemistry Suite (ACS) instru- ment onboard the ExoMars Trace Gas Orbiter (TGO) ESA-Roscosmos mission has per- formed Solar occultation measurements of the Martian atmosphere in the 2.3–4.2 μm spectral range since March 2018, which now covers two Martian Years (MY). We use the methodology previously developed for the study of the MY 34 Global Dust Storm (GDS) (Stcherbinine et al., 2020) to monitor the properties of the Martian water ice clouds over the first two Martian years covered by ACS-MIR (effective radii, extinction, altitude). The observations encompass the period Ls = 163◦ in MY 34 to Ls = 181◦ in MY 36. We determine that the typical altitude of the clouds varies by 20 to 40 km between the summer and winter, with a maximum extension up to 80 km during summer in the mid- latitudes. Similarly, we also note that for a limited temporal range, the altitude of the clouds also varies by 20 to 40 km between the polar regions and the midlatitudes. We also compare observations acquired during the MY 34 GDS to observations from the same period in MY 35, using that latter as a reference to characterize the effects of this GDS on the clouds’ properties. In addition, we compare our retrievals with the predictions of the Mars Planetary Climate Model (PCM), which shows a reasonable agreement over- all for the altitude of the clouds, although the model usually predicts lower altitudes for the top of the clouds.

Domaines: Planète et Univers [physics]

Aurélien Stcherbinine, Franck Montmessin, Mathieu Vincendon, Michael J. Wolff, Margaux Vals, et al.. A Two Martian Years Survey of Water Ice Clouds on Mars with ACS onboard TGO. 2022. ⟨insu-03908848v1⟩