Water vapor mapping on Mars using OMEGA/Mars express

Abstract A systematic mapping of water vapor on Mars has been achieved using the imaging spectrometer OMEGA aboard the Mars Express spacecraft, using the depth of the 2.6 μm ( ν 1 , ν 3 ) band of H 2 O. We report results obtained during two periods: (1) Ls=330–40° (January–June 2004), before and after the equinox, and (2) Ls=90–125°, which correspond to early northern summer. At low latitude, our results are globally consistent with previous measurements from ground-based and space (MAWD/Viking and TES/MGS) observations. However, at early northern summer and at high northern latitude (70–80 °N), the water vapor abundances, which we retrieved, appear to be weaker than MAWD and TES results. At the time of water sublimation during early northern summer, there is a maximum of water vapor content at latitudes 75–80°N and longitudes 210–24°E. This region is not far from the area where OMEGA identified a high abundance of calcium-rich sulfates, most likely gypsum. Our data provide the first high-resolution map of the martian water vapor content above the northern polar cap.