EARTH ANALOG FOR RECENT FLOWS AND HIGH-LATITUDE LANDFORMS ON MARS: ICY DEBRIS FANS IN THE WRANGELL VOLCANIC FIELD, ALASKA

New Mars Reconnaissance Orbiter HiRise and CRISM imagery of polar layered terrain of Mars reveals striking similarities to icy debris fans along the base of steep escarpments in Alaska formed in high-latitude periglacial environments. Process and morphologic observations of a deglaciating site in the Wrangell Mountains reveal a complex suite of supraglacial processes involved in the construction of icy debris fans. Snow, ice, and sediment are delivered to the fans from degradation of an upper-level icecap, now detached from a remnant cirque glacier, by a combination of rockfall, avalanche, and icy debris flow processes. Icy debris flows in Alaska produce morphologies similar to modern flows recently documented on Mars; a process analog for active water-and ice-rich flows on Mars in settings other than polar regions, such as crater walls. Alaskan icy debris fans were studied during an 8-day reconnaissance mission in July 2006, when 289 major depositional events; including icy debris flows, snow/ice avalanches, rockfalls, small jokulhlaups, and glacial calving, were directly observed. Process dominance varies between fans. Fans with larger catchments receive episodic icy debris flows triggered by outburst flows that mobilize rockfall sediment temporarily stored in catchments above the fan apex. Fans with smaller catchments have better linkage to the upper icecap, providing a direct pathway for frequent large avalanches. Avalanche-dominated fans thicken rapidly from an overabundance of snow/ice supply to the point where they become hybrid fan-glaciers. Surficial geology evolves rapidly in this high-latitude environment through both depositional events and solar-driven albedo changes that occur daily. Ground penetrating radar surveys show that subsurface sedimentary architecture and fan evolution is similar to the active surface processes and deposits observed on the fans. Icy fans in Alaska are sourced by degradation of an icecap that has recently become detached from a remnant cirque glacier during accelerated warming. Similarly, fans in the polar layered terrain of Mars appear to be forming by processes related to the degradation of ice-rich layered escarpments. Direct field observations of active geomorphic processes provide unique insights on the pace and nature of high-latitude landscape evolution during climate changes on both planets.