DPS 35th Meeting, 1-6 September 2003
Session 14. Mars Atmosphere II
Poster, Highlighted on, Wednesday, September 3, 2003, 3:00-5:30pm, Sierra Ballroom I-II

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[14.23] Water Vapour Variations in the Martian Atmosphere: Phobos-2 Infrared Spectrometer (ISM) data reanalyzed based on improved topography data (MOLA/MGS)

S. Werner, D. Titov (MPAE), S. Erard, J.P. Bibring (IAS)

The water vapour content of the Martian atmosphere is one of the main topics in the research on this planet. Water vapour is the minor constituent of the Martian atmosphere with the highest variability. Its seasonal and latitudional variations reach a factor of 10. In addition, diurnal variations and variations correlated with the properties of the Martian surface are observed. Also the vertical distribution of this gas is variable. These variations are caused by sublimation and condensation of the polar caps and surface frost, adsorption to and desorption from the surface regolith, and advective transport of the gas due to the global circulation. Both, seasonal changes and diurnal and spatial variations imply that exchange of water vapour between atmosphere and the regolith of the Martian surface plays a major rôle in explaining the variations of atmospheric water vapour. The imaging infrared spectrometer (ISM) of the Phobos-2 spacecraft provided spectra in the wavelength range of 0.8--3.5 10-6m. Very high signal-to-noise ratio allows one to study variations of weak spectral features of atmospheric H2O. Unfortunately, they overlap with the spectral bands of the dominant constituent of the Martian atmosphere, carbon dioxide. Using high resolution data of the Martian surface's topography provided by the Mars Orbiter Laser Altimeter (MOLA, Mars Global Surveyor) to calculate the CO2 column density the ISM spectral data are reanalysed. The main goal of this investigation is to study spatial variability of the atmospheric water vapour abundance and its correlation with topography and surface properties. This will provide a clue to the mechanism of H2O exchange between atmosphere and regolith. As an example data observed above the Tharsis volcanoes are compared to data measured above the surrounding planes.

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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.