Modeling the HDO cycle in the Martian atmosphere.

International audienceAmong all the deuterated species of water, HDO has received much attention from scientists since its early measurement in the Martian atmosphere. Its current concentration, compared to terrestrial standards, suggests a significant loss of water that has escaped to space in the past. The study of HDO is intimately related to the past abundance of water and is therefore useful for understanding Mars' climate. As a first stage of a future modeling of atmospheric Deuterium (involving photo-chemical processes presently unaccounted for), we will present results from a GCM-based modeling of the HDO cycle. Significant seasonal and geographical variations of the HDO/H2O ratio are expected due to severe fractionation during condensation processes. Comparison with available measurements will be discussed