A mapping of martian water sublimation during early northern summer using OMEGA/Mars Express

The OMEGA imaging spectrometer aboard Mars Express has been used to map the water vapor abundance over the martian surface, from the analysis of the 2.6 μm band of H₂O. As a preliminary result of this study, we present water vapor maps in the northern hemisphere at the time of the northern polar cap sublimation (Ls = 94-112 deg). The maps show a mean H₂O mixing ratio of about 2-3 × 10^-4 at a latitude of 40N, and in the range of 5 × 10^-4-10^-3 at 60N-80N latitudes. The corresponding mean H₂O column densities are about 25 pr-μm at 40N and between 40 and 60 pr-μm at 60N-80N, with uncertainties of about 30 percent. Our results are in agreement with previous results by MAWD/Viking and TES/MGS for latitudes up to 60N, but seem to indicate lower values at high latitude. However they are still globally consistent in view of our error bars.