D and H in the Lower and Upper Atmosphere of Mars

Abstract:

The water cycle in the near-surface region of Mars is coupled to the lower atmosphere via multiple mechanisms that include seasonal dust and circulation driven processes. The variability of water and its isotopologue, HDO, vary similarly and with similar patterns near the surface as well as at altitudes up to 80 km. At higher altitudes, water molecules are broken down into atoms. Measurements of H and D, made in the upper atmosphere of Mars show variations that differ from their lower altitude parent molecules. Observations of H and D, made by the MAVEN mission, spanning four Mars Years are analyzed. Preliminary results indicate that the water-originating atoms in the upper atmosphere are decoupled from water molecules at lower altitudes. These findings can inform the water cycle on present day Mars, and provide improved estimates for water loss from the planet.