High-altitude CO₂ clouds on Mars: OMEGA and HRSC observations

Anni Määttänen (1) , Franck Montmessin (1) , B. Gondet (2) , H. Hoffmann (3) , F. Scholten (3) , E. Hauber (3) , F. Gonzalez-Galindo (4) , F. Forget (4) , J.-P. Bibring (2) , Jean-Loup Bertaux (1) , G. Neukum (5)

1 PLANETO - LATMOS
2 IAS - Institut d'astrophysique spatiale
3 DLR - Deutsches Zentrum für Luft- und Raumfahrt
4 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)
5 Freie Universität Berlin

The Martian climate hosts a rare phenomenon of condensation of the bulk atmosphere. CO₂ condenses on the polar ice caps, but also forms clouds in the atmosphere. The existence of low-level, convective CO₂ clouds in the polar night was indirectly discovered by MOLA [1,2] and modeled in some studies [3-5]. Recently several satellite instruments [6-9] have observed CO₂ clouds also near the equator, but at high altitudes where the temperatures are low enough for CO₂ condensation. Montmessin et al. [7] identified spectroscopically from MEx/OMEGA observations these high-altitude clouds to be composed of CO2 ice crystals by modeling the CO2 ice spectral signature that was observed in a deep CO₂ gas absorption band at around 4.3 μm. In this work we have used the OMEGA [10] and HRSC [11] observations to map the occurrences of the high-altitude CO₂ clouds and their properties. We have also compared the observations to the predictions of the LMD Mars Global Climate Model (LMD-MGCM) [12] and in particular its improved version that extends to the upper atmosphere [13].

Domaines: Planétologie et astrophysique de la terre [astro-ph.EP]; Planétologie et astrophysique de la terre [astro-ph.EP]

Anni Määttänen, Franck Montmessin, B. Gondet, H. Hoffmann, F. Scholten, et al.. High-altitude CO₂ clouds on Mars: OMEGA and HRSC observations. Third International Workshop on Mars Polar Energy Balance and the CO₂ Cycle, Jul 2009, Seattle, WA, United States. pp.37-38. ⟨hal-00484879⟩