No abstract

[1] We investigate the surface morphology of a study area in western Utopia Planitia, Mars, which is characterized by a variety of landforms that resemble those of terrestrial periglacial landscapes. Polygonally fractured ground and thermokarst-like depressions are found to be located in a young mantling deposit with a thickness of several tens of meters. We observe a latitudinal dependence of the degradation of this mantling deposit. Larger depressions, whose floors reveal the underlying basement rocks, cover a higher fraction of the total terrain in the southern part of the study area than in the northern part, indicating a more intense degradation of the mantle in the south. All depressions have an asymmetric cross section in north-south direction, interpreted to be the result of the different solar radiation on differently oriented slopes. On the basis of our morphological observations, we develop a conceptual model for landscape evolution in western Utopia Planitia. It involves subaerial deposition of a layered, ice-rich mantle and its subsequent degradation by polygon formation and sublimation. A terrestrial analog to the polygonally fractured mantling deposit and its thermokarst-like depressions is the Siberian Ice Complex or ''Yedoma,'' which consists of subaerial ice-rich deposits and is connected to nonglaciated landscapes with highly continental cold-climatic environmental conditions. Our comparison suggests that no unusual or exotic processes need to be invoked to explain the current morphology of western Utopia. However, the young age of the deposition and degradation implies climatic excursions in the very recent past on Mars.

[1] On the basis of High Resolution Imaging Science Experiment (HiRISE) images of two successive years we observed changes of a gully on the Russell crater dune field. Within the first year the length of a ∼2 m wide incised gully channel grew about 50 m downslope, and ∼120 m within in the second year. Gully activity occurred in early spring between L S ∼198°and ∼218°in the first year and between L S ∼192°and ∼221°in the second year. Based on the channel morphology, spectral data and modeled surface temperatures, the changes can be best explained with transient melting of small amounts of H 2 O-ice triggering slurry flows consisting of sand mixed with liquid water. Citation: Reiss, D., G. Erkeling, K. E.Bauch, and H. Hiesinger (2010), Evidence for present day gully activity on the Russell crater dune field, Mars, Geophys. Res. Lett., 37, L06203,

No abstract