Periglacial Features on Earth (Siberian Arctic) and Possible Martian Analogues: Quantitative Morphology of Patterned Ground and Thermokarst Structures

Kurzfassung

Periglacial surface structures like ice wedge polygons and thermokarst depressions are widely distributed in Siberian permafrost landscapes. Features of comparable morphology occur also on the Martian surface, especially in mid-latitude regions. We present polygon structures and thermokarst phenomena of different shapes and sizes, which were observed within the last four years during several German-Russian expeditions in Northern Yakutia. The morphology of the structures is studied quantitatively by air-borne and satellite imagery. Additionally, the geological and hydrological conditions for the formation of the periglacial features are described. Similar quantitative analyses of Martian analogue features have been carried out in order to obtain information on the lithological and hydrological environment in which they formed. These structures are often situated close to the mouths of the large outflow channel systems on Mars. Therefore, it is assumed that water from the flood events that carved the outflow channels oozed away into the ground forming a permafrost layer. Depth and thickness of this layer is not known. A model derived from rampart crater data (see Costard & Kargel, Icarus 114, 1994) for the ice content in Acidalia Planitia, proposes a ground ice layer > 2500 m thick below a layer of fluvial sediments containing ice segregations ~ 940 - 1000 m thick. By comparing the results of both terrestrial and martian investigations we will try to draw conclusions for the genesis of the observed structures on Mars as well as the depth and thickness of the possible permafrost layer.