MORPHOCLIMATE ZONATION IN THE ANTARCTIC DRY VALLEYS: IMPLICATIONS FOR ASSESSING CLIMATE CHANGE AND NEAR-SURFACE ICE ON MARS

The Dry Valleys region of Antarctica (ADV) is generally classified as a hyper-arid, cold-polar desert. The region has long been considered an important terrestrial analog for Mars because of its generally cold-and-dry climate and because it contains a suite of landforms at macro-, meso-, and microscales that resemble closely those observed on the Martian surface. The ADV region includes at least three microclimate zones: a coastal thaw zone, an inland mixed zone, and a stable upland frozen zone; zones are defined on the basis of varying atmospheric temperatures, soil moisture, and relative humidity. Subtle variations in these climate parameters during summer months result in considerable differences in the distribution and morphology of: 1) gullies (macroscale features); 2) polygons, including ice-wedge, sand-wedge, and sublimation-type polygons, as well as viscous-flow features, including solifluction lobes, gelifluction lobes, and buried glaciers (mesoscale features); and 3) variations in rock-weathering processes/features, including salt weathering, thermals stress, wind erosion, and desert varnish (microscale features). Equilibrium landforms are those features that formed in balance with climate conditions in existing microclimates. Some equilibrium landforms, such as sublimation polygons, register the presence of extensive near-surface ice; identification of similar landforms on Mars may also herald the location of shallow ice.

Identification of overprinted equilibrium landforms in the ADV suggests former shifts in climate zonation and may help to predict future landscape change in the ADV. This type of landform analyses can be applied to Mars where roughly similar microclimates and suites of equilibrium landforms occur at different latitudinal bands and at different times during Mars's history. An important aspect of the stable upland zone in the ADV is the long-term preservation of near-surface buried ice. We are currently testing various drill technologies to sample this ice. Further, we are examining and monitoring the thermal properties and mineralogical characteristics of the sublimation tills that overlie this ice in order to help provide a quantitative assessment of ice stability in the ADV and, by extension, on Mars.