Water vapour On Mars from Mars-Express PFS and OMEGA measurements

Introduction: The water cycle is a key element of the martian climate, involving interactions between atmospheric reservoirs (water vapor, clouds), surface reservoirs (polar caps and perhaps permafrost), and atmospheric dust. Extensive monitoring of the water cycle has been performed in the past, primarily from Viking/MAWD (Jakosky and Farmer 1982), MGS/TES (Smith 2002, 2004), and with contributions from ground-based observations in the visible and millimeter wavelengths. While the main features of the water cycle are now understood for the most part (e.g. Montmessin et al. 2004), some aspects need to be observationally better characterized, e.g. the inter-annual variability, the geographical distribution of water, the details of the onset of the sublimation in the polar caps, and the vertical distribution of water as a function of season. Observations and goals: Mars Express carries three instruments capable to map and monitor the water vapor content of the Martian atmosphere: SPICAM – at 1.38 μm, OMEGA – at 2.56 μm and PFS – at 2.56 μm and 3050 μm. We will present results based on PFS and OMEGA data. We will focus on 1. The inter-comparison between results obtained from the two instruments, and from the different wavelength range. 2. The longitudinal distribution of water vapor at mid-latitudes and its relation to atmospheric dynamics and potential subsurface sources 3. The spatial distribution in polar regions during periods of water maximum 4. The vertical distribution of water 5. The HDO abundance and the search for possible variations in the HDO/H2O ratio