THERMOKARST DEGRADATION OF POTENTIAL ICE-WEDGE POLYGONS INSIDE SCALLOPED DEPRESSIONS IN UTOPIA PLANITIA, MARS. A. Séjourné

Introduction: An assemblage of possible periglacial landforms dots the landscape of western Utopia Planitia in the northern mid-latitudes of Mars. The landforms comprise flat-floored depressions with scalloped shapes [1-6]; spatially-associated patterned ground [2-4, 7]; and polygon-junctions pits [3, 8, 9]. In the last few years, several papers point to a thermokarst origin of the scalloped depressions, i.e. degradation of ground-ice [1-5]. Development of these depressions has been explained by two contrary models. The first one suggests a poleward expansion [2-3].; the second one suggests an equatorward expansion [4, 6]. Here, we describe new landforms resulting from the degradation of polygons on the pole-facing slopes of scalloped depressions. In order to understand the processes of degradation, we compare these landforms with active thermokarst landforms occurring along thermokarst lakes in Central Yakutia (Siberia).