Introduction: The McMurdo Dry Valleys of Antarctica have commonly been used as an analog for Mars; analogies are due in part to the regions hyperarid and cold climate as well as its abundance of similar-appearing microscale and macroscale morphological features such as gullies, lineated valley fill, and polygons [eg. 1,2,3]. With the recent direct observations of water ice on Mars from the NASA Phoenix lander and MRO Satellite images [4], a complete understanding of the physics of buried-ice preservation in Antarctica is becoming increasingly important in helping to model the stability and age of buried ice deposits on Mars. Geological Setting: Beacon Valley, Antarctica is an ideal site for investigating the preservation of ancient ice buried beneath a variety of surface deposits and morphologies [5]. The Mullins Valley alpine glacier, which occupies a tributary valley to Beacon Valley, is a slow-moving-to-stagnant cold-based glacier. Its capping sublimation till is composed of dolerite-and-sandstone clasts set within a sand-rich matrix (Dolerite Till). Collectively, the till is approximately 10 to 15 cm thick in the upper ablation zone and thickens to ~50 cm towards the terminus of the glacier. The top 10 cm is slightly oxidized [6]. Insitu overlying ashfall deposits at the terminus have been dated at ~7.9 Ma [7]. Alternative methods for determining the chronology of the glacier include: cosmogenic nuclide dating of surface rocks, integrated flow from synthetic aperture radar interferometry, numerical glacial modeling, and direct dating of atmospheric gases within the ice [eg. 7-9]. Polygons at the till surface mature with increasing distance down glacier. In some portions of central Beacon Valley, stagnant, buried glacier ice is derived from an ancient advance of Taylor Glacier, an outlet glacier from the East Antarctic Ice Sheet, up into Beacon Valley, rather than from expansion of Mullins Glacier. The remnant stagnant lobe ice is protected by a ~50-cm thick, silt rich sublimation till (Granite Drift) with clasts of dolerite, sandstone, and granites; the latter are not native in Beacon Valley. Here the polygons are fully mature and troughs can reach 2-3 meters in depth. Methods: Vapor flux in sublimation till is governed primarily by two mechanisms: molecular diffusion of vapor in pore spaces and advection of air Fig. 1. Till and surface textures in Beacon Valley. a) Dolerite Till of fresh dolerite clasts and minimal sands. b) Granite Drift with a silt and sand rich matrix. c) Desert Pavement displaying interwoven and highly weathered clasts.

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 …

Introduction: The discovery of gullies on Mars attracted significant attention because of the apparent role of liquid water in their formation and because of their very youthful nature [1,2]. They were initially interpreted to be the result of groundwater discharge [1-3], though further considerations regarding the current metastability of liquid water on the surface of Mars generated alternative explanations, including atmospherically deposited sources of water [4-7]. Recent modeling work has demonstrated that snowfall [8] and the melting of such deposits [4,5,9] is possible in the regions where gullies are located under periods of higher obliquity. This has provided support for the snowmelt model of gully formation [4-6,9]. The utilization of terrestrial analogs provides an essential natural laboratory for testing the snowmelt model as a viable means of gully formation. In this analysis we report on results obtained from field studies within the McMurdo Dry Valleys of Antarctica (ADV), a hyper-arid polar desert that has long been held as one of the most Mars-like of terrestrial analogs [10-12] (Fig. 1). Within this environment, precipitation only falls as snow and so the availability of liquid water is restricted to meltwater generated by the solar heating of ice and snow deposits. In order to best constrain the Martian conditions we concentrated our efforts within the most elevated (and hence driest) portion of the intermediate microclimate zone [12] situated within the South Fork (SF) region of upper Wright Valley. This region marks the most inland extent of active fluvial features within the ADV and is most analogous to Mars during Amazonian periods of high obliquity in terms of precipitation and max T values [12] (Fig.1). Unlike other gullied regions of the ADV, there are no significant adjacent glacial systems to supply meltwater, and so the most significant ice deposits are snowbanks that more closely resemble the deposits predicted to form on Mars during its recent history [4-6,9]. We found that there is significant inter-annual variability in the abundance of snow for gully generation. However, even in years with minimal snowfall, windblown snow can be concentrated in suitable geomorphic traps. 2006-07: The 'Wet' Year. The majority of the larger gullies studied in SF in 2006-7 exhibited fluvial activity associated with snowmelt from within two geomorphic traps: Alcoves. The northern edge of the Asgard Mountains in SF contains a number of alcoves along

Introduction: One of the major surprises of the Mars Global Surveyor mission was the discovery of gullies, a class of unusually young features consisting of an alcove, a channel and a fan [1-2]. These features were interpreted to have originated through the flow of liquid water originating from groundwater discharge [1,2], although alternate interpretations have been presented [see 3]. Uncertainty as to the possibility of surface water flow under current martian conditions (below the triple point of H2O) and evidence that conditions might have been more conducive to melting during higher obliquity conditions in the past, led to the idea that these features might be relict. Recent repeat observations of gullies, however, are interpreted to mean that at least some gullies are currently active [4], and this has intensified the discussion concerning their formation mechanisms and age. In order to look for changes since 2000 that might indicate the presence of fluid flow in gully channels, Malin et al. [4] repeatedly imaged thousands of gullys at hundreds of different sites; they ultimately found only two sites at which changes could be documented. These changes included the appearance of light-toned flows that formed at the two locations sometime between the two imaging sequences (8/99-2/04 and 12/01-5/05). On the wall of the crater at the Terra Serenum site a distinct light-toned flow appeared in the channel. On the southern wall of a crater at Centauri Montes, light-toned material flowed down the slope and formed a deposit. The two new deposits have similar apparent brightness, and relatively long, extended digitate distal and marginal branches; they flow down 20-30 slopes, have relatively low relief and divert around obstacles [4]. These characteristics suggest that the material moved slowly, thinned while flowing, and branched easily [4]. Malin et al. [4] interpreted these characteristics to mean that the observed deposits were formed by flow of fluidized material through the gullies to their aprons by release of groundwater from underground aquifers "initiated and fed by the collapse of an ice-impregnated rock dam creating a brief, low-volume debris flow initially charged with liquid but in which ongoing freezing at both the top and bottom surfaces, bed infiltration, and incorporation of slope sediment and debris increases viscosity, which inhibits downslope and runout motion" [4]. Because the light tone has lasted more than a martian year in an environment where water ice is unstable, Malin et al. [4] suggest that the brightness may reflect "replenishment of surface frost by exhalation, elutriation of fine-grained sediment, or precipitation of salts" [4]. Malin et al. [4] conclude that water flowed on the surface of Mars during the last decade and that it was released from an underground aquifer source. Terrestrial analogs to martian environments may provide insight into the processes operating on Mars, and the origin and life cycle of gullies. Here we report on the results of ongoing field studies of gullies in the Antarctic Dry Valleys (ADV), a hyperarid cold polar desert analog for Mars [7]. We address the questions: What is the life cycle of gullies and what processes are responsible for their later stages? How does the ADV insight help to evaluate and understand the evidence [7] for current gully activity on Mars?

2143, Seventh International Conference on Mars 3059.pdf

problems by building a considerable number of new houses and very effective slum clearance drive. One of the many tragedies of the war was that, as all energies, wealth and resources were concentrated on the prosecution of a successful campaign in the interest of the survival of our way of life, vital social services, such as housing, were retarded and became non-existent during the period of hostilities. If the impetus of the attack upon slums by demolition and reconditioning, and the speedy building of new houses which we experienced before the war had been allowed to continue for another five years, we would have certainly been within measurable distance of solving most of our housing problems. Locally, we had made demolition and clearance orders involving 773 houses ; 125 houses have been reconditioned and general repairs carried out to hundreds more. During the same period we built 1,658 new houses. Had this progressively increasing tempo of our activities been allowed to continue into a second five years, then I have no hesitation in claiming that housing