South Pole of Mars : a dynamic history of ice and dust

Séminaire IPAG de Sylvain Douté (IPAG), jeudi 23 mars 2017 à 11h00, IPAG seminar room

On Mars CO2 is a major component of the atmosphere whether in the gaseous state (abundance of 95%) or in the solid state forming clouds at high altitudes. During winter, up to 30 % of the atmospheric CO2 condenses or precipitates at the surface to form seasonal polar deposits. They completely sublimate in spring, except in the South pole where a residual cap persists during summer. Recent studies have shown that the sublimation of these condensates causes the erosion of their substratum, the functioning of dusty plumes and the triggering of avalanches on the slopes. Thus, the Martian CO2 is suspected of being a significant geological agent at present. In spring the seasonal deposits also control the dust activity in the south polar atmosphere. A prominent dust collar encircles the polar cap and local dust storms generated in this region sometimes develop to global storms. In turn, dust settling or removal linked with the atmospheric dynamic greatly modify the bolometric albeo of the ice, a key parameter to calculate the energy balance of the icy deposits, and thus their evolution. During the seminar, in the context of the ongoing space missions, I will present my contribution to research efforts aimed at understanding the complex interplay between the CO2 deposits, the dust, and the atmosphere.