THERMOPHYSICAL AND MORPHOLOGICAL ANALYSIS OF ICE-RELATED MODIFICATION IN THE NORTHEASTERN ARGYRE BASIN, MARS

Ancient Martian highlands, in places sculpted by fluvial processes, have subsequently undergone alteration by glacial/periglacial, aeolian and mass-wasting processes. The rim of the Argyre impact basin in the southern hemisphere has experienced a complex history of modification since its formation. This study examines surficial characteristics for a portion of the northeastern edge of the rim in order to better understand the history of modification and the role volatiles have played.

Surface morphologies are examined using high resolution visual images taken by the CTX (~6m/pixel) and HiRISE (<1m/pixel) instruments onboard the Mars Reconnaissance Orbiter. Thermophysical properties of the surface (related to particle size, packing, and degree of induration) are analyzed by identifying differences in temperature and/or thermal inertia derived from night time infrared images (100m/pixel resolution) from the Thermal Emission Imaging System (THEMIS), onboard Mars Odyssey.

The associated highlands exhibit downslope deposits with viscous flow features surrounding isolated massifs and plateaus. Some topographic highs exhibit gully formations and alcoves that transition to lobate deposits down slope. Groups of gullies can be seen emanating from flow features, but others are superposed on these features suggesting that they are more recent. Linkages of lobate deposits may adjoin similar deposits from opposing ridges to form lineated valley fill, usually with a distinct termination: these types of features are typically interpreted to be analogous to terrestrial debris-covered glaciers. Thermophysical variations on the surface of these features and at their ramparts appear to be related to flow processes. These are interpreted to represent differences in particle size related to the flow mechanisms that formed the features. Overlying and adjacent surfaces often exhibit a pit-and-butte texture that may be related to sublimation of subsurface ice. Much of the region is overprinted by evidence of aeolian activity, such as sand dunes and dust devil tracks. A variety of erosional processes have been active on this region over geologic time. These observations offer important implications for the influence of subsurface volatiles (past and present) on the landscape.