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 ( ν₁, ν₃) band of H ₂O. 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.