Mars' "White Rock" feature lacks evidence of an aqueous origin: Results from Mars Global Surveyor

The "White Rock" feature on Mars has long been viewed as a type example for a Martian playa largely because of its apparent high albedo along with its location in a topographic basin (a crater). Data from the Mars Global Surv eyor Thermal Emission Spectrometer (TES) demonstrate that White Rock is not anomalously bright relative to other Martian bright regions, reducing the significance of its albedo and weakening the analogy to terrestrial playas. Its thermal inertia value indicates that it is not mantled by a layer of l oose dust, nor is it bedrock. The thermal infrared spectrum of White Rock s hows no obvious features of carbonates or sulfates and is, in fact, spectra lly flat. Images from the Mars Orbiter Camera show that the White Rock mass ifs are consolidated enough to retain slopes and allow the passage of salta ting grains over their surfaces. Material appears to be shed from the massi fs and is concentrated at the crests of nearby bedforms. One explanation fo r these observations is that White Rock is an eroded accumulation of compac ted or weakly cemented aeolian sediment.