The Use of Equilibrium Landforms to Identify Recent Climate Change on Mars: Insights from Field Studies in the Mcmurdo Dry Valleys of Antarctica

Introduction: The recognition of groups of terrestrial climate-related landforms has led to the definition of different morphogenetic regions [e.g., 1-2] which have been classified in terms of both mean annual temperature and precipitation. Marchant and Head (2007) [3] used this approach to classify the McMurdo Dry Valleys of Antarctica (ADV) into three separate microclimate zones based on groups of distinct equilibrium landforms which are in balance with local environmental conditions. Through the morphological mapping of the ADV, they were able to discern past and/or ongoing shifts in climate zonation from the identification of landforms that today appear in dise-quilibrium with local microclimate conditions [3]. The ADV are a hyperarid, cold polar desert in which sub-limation exceeds precipitation [3] and has thus long been held to provide one of the closest terrestrial ana-logs for current Martian conditions [4-5]. Hence the methodology applied by [3] provides a framework from which to assess the climate history of Mars. Here we report on our morphological investigations of an unnamed martian crater depression located at 40°S, 5°E. The site exhibits a multitude of ice-associated landforms of various scales and has a high degree of data coverage from all of the Mars orbital instruments. Hence, it is an excellent site in which to apply the methodology of [3] in order to gain insights into both the local and global climate histories of Mars. To aid our interpretation of the martian landforms, we draw upon fieldwork conducted in the ADV during the austral summers of 2006-7 and 2008-9. Antarctic Dry Valleys: Fieldwork was carried out in the different microclimate zones in order to locate and identify landforms both active and relict that are morphologically similar to those in the Mars study site. Upland Stable Zone [3]: In Beacon Valley, relatively small-scale glaciers form on steep walls as plateau ice collapses as shown in Fig. 1. Rock-fall debris is also supplied to the surface of the glacier from intervening cliffs. Ice-cored moraines fringe the present ice margin. Beyond these moraines are ice-cored lobes, which presumably represent downslope flow of older (distal) ice-cored moraines. Inland Mixed Zone [3]: A 7+ km long debris-covered viscous-flow tongue occupies a major trough in the South Fork of Upper Wright Valley (Fig. 2). The snout of the tongue exhibits a convex up profile which levels off around ~20 m above the valley floor. The lack of a steep terminus and its convex-up cross …