Ninth International Conference on Permafrost ... - IARC Research

The Microtopography of Periglacial Landforms on MarsNicolas MangoldLaboratoire IDES, CNRS and Université Paris Sud, 91405 Orsay, FranceIntroductionThe planet Mars is covered by many landforms involvingwater ice, either at surface or at depth. These landforms areimportant in studying the geographic distribution of waterice, its temporal variation, and the possibility of freezethawcycles in past epochs. Geologically recent Martianhillside gullies, discovered in Mars Orbiter Camera (MOC)Narrow Angle (NA) images (Malin & Edgett 2000), exhibitcharacteristic morphologies similar to terrestrial debrisflows in mountain or arctic regions, formed by flowing wateror water-rich slurries, leading Malin and Edgett (2000) tosuggest that they, too, were formed by the action of water.Processes other than water erosion have been proposed toexplain the formation of gullies, including the action ofCO2-based debris flows (e.g., Musselwhite et al. 2001) andgranular avalanches or mass wasting of CO2 frost (e.g., Ishii& Sasaki 2004). The role of liquid water is still debated,especially given the subfreezing mean temperature (-60°C)that might only reach submelting temperatures during highobliquity periods of the past (Costard et al. 2002). The originof the fluid is also questioned. Various mechanisms for theformation of gullies by water have been proposed, althoughfundamentally they can be divided into either atmosphericor groundwater processes depending on the source of thewater.Until recently the only available images with sufficientresolution to detect gullies have been MOC NA data, andmost previous studies have used this dataset. However,the HiRISE camera of the Mars Reconnaissance Orbiterprovides high resolution (