HR: 08:50h
AN: H31G-03 INVITED     [Abstracts]
TI: Geomorphic Processes and Cold-Based Glaciers in the Antarctic Dry Valleys: Implications for Glaciation and Climate Change on Mars
AU: * Marchant, D R
EM: marchant@bu.edu
AF: Boston University, Department of Earth Sciences, Boston, MA 02215 United States
AU: Head, J W
EM: James_Head@brown.edu
AF: Brown University, Department of Geological Sciences, Providence, RI 02912 United States
AB: The very low atmospheric temperatures and limited availability of liquid water in Earth's polar deserts make for compelling comparisons to a dry and cold Mars. Among polar deserts on Earth, the Dry Valleys region of Antarctica has long been considered as the most Mars-like. Classified broadly as a cold and hyper-arid region, the valleys display a diverse suite of surface landforms that provide a geomophological framework for interpreting features on Mars. New climate and geomorphological data from the Dry Valleys show that the region is best subdivided into a series of narrow climatological zones. Each microclimate zone differs from the next by slight variations in atmospheric temperature and soil-moisture. Along microclimate boundaries, subtle variations in temperature and soil-moisture are sufficient to produce remarkable variations in surface topography and geomorphic process. As is the case for most polar deserts, the geomorphic impact of minor variations in soil moisture and temperature is disproportionately large when compared to similar shifts in humid-temperate latitudes. Insight gained from the distribution and temporal migration of microclimate zones in the Dry Valleys may help shed light on the origin and, in particular, the evolution of glacial and periglacial features and climate change on Mars. Glaciers with basal temperatures well below the pressure melting point have been one of the hallmarks of the western Dry Valleys region since at least late Miocene time. These so called cold-based glaciers are generally non-erosive and tend to preserve underlying landscapes. Supra-and englacial debris carried by such glaciers is commonly deposited at the glacier snout, generally as a series of linear drop moraines. Debris-covered glaciers may form in cases where excess sublimation brings englacial material to the ice surface, forming a protective sublimation till that slows the loss of remaining ice. In several places, the martian surface shows a suite of deposits that closely resemble those associated with cold-based glaciers on Earth. Foremost among these places are lobate deposits along the northwest flanks of the Tharsis Montes as well as the Deuteronilus region. These results, along with new insights from quantitative measurements of glacial abrasion have prompted us to re-evaluate some Martian landforms in terms of glacial processes. As background, we here summarize the formation of drop moraines and sublimation tills associated with cold-based glaciers in the Dry Valleys of Antarctica, and then outline the case for similar glacial landforms on Mars.
DE: 5415 Erosion and weathering
DE: 5416 Glaciation
DE: 5462 Polar regions
SC: Hydrology [H]
MN: Fall Meeting 2005