Mars CO2 ice clouds: results of 4 Martian years of monitoring by OMEGA/Mars Express
Abstract
An important achievement of the ESA/MarsExpress mission is the detection and characterization of mesospheric CO2 ice clouds, by indirect (PFS and SPICAM) and direct (OMEGA and HRSC) observations, as discussed by Clancy et al.. These clouds have been recently detected by CRISM and MCS on board MRO. Back in 2007, OMEGA provided the first non ambiguous discovery and characterization of high altitude CO2 ice clouds in Mars atmosphere, at specific locations and times, through their diagnostic reflectance signature at 4,26 m. They were monitored, in their space/time evolution, during 4 consecutive Martian years. They offer a unique possibility to understand the processes involved in cloud formation, both on Mars and Earth. We will present an overview of the properties of these clouds in terms of location, altitude, seasonal variation, and opacity. Although no definite explanation for their formation can be proposed yet, we will suggest potential processes and conditions to account for.