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J. L. Benson (University of Toledo), D. A. Glenar (NASA GSFC), P. B. James (University of Toledo), M. D. Smith, J. C. Pearl (NASA GSFC), M. J. Wolff (Space Science Institute), S. C. R. Rafkin (Southwest Research Institute)
Topographic water ice clouds dominate the Martian aphelion season cloud band, which typically appears between Ls = 40 and 150. Aerosol properties of such clouds have been documented at large scales, however little emphasis has been placed on examining the spatial fine-structure of cloud properties. Such measurements should reveal the true extremes in cloud optical depth, particle size and water ice content, and observationally constrain cloud growth models that attempt to include both the daily atmospheric water cycle and small-scale topography.
We use MOC wide-angle (WA) Daily Global Maps supported by TES dust opacity measurements and radiative transfer models to retrieve and map cloud properties at the MOC WA spatial resolution of 7.5 km. TES dust measurements are adjusted for wavelength using up-to-date aerosol models, and corrected for topography using MOLA data. Preliminary results from a cloud near Ascraeus Mons at Ls = 81 reveal an optically dense region having dimensions of a few 10’s of kilometers. Water ice particle size and cloud water content are constrained using a combination of TES and MOC WA blue measurements. Cloud top height is estimated by documenting the location of cloud intersects with the surrounding MOLA-derived topography.
Calibrated MOC/TES data span approximately 1.6 hours of local time, thus enabling the study of diurnal cloud evolution during the rapid afternoon growth period. MGS coverage is supplemented by data from the THEMIS multi-band thermal imager, which extends the time window to over three hours when concurrent THEMIS data are available. Seasonal and interannual cloud variability will also be investigated.
This work is supported by the NASA Mars Data Analysis Program.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.