2 Gasselt, Stephan van 2007 Geosciences Berlin Free University Berlin 292 Mars, periglacial geomorphology, pingos, polygons, topography, Remote sensing, This work covers the dominant aspects of landforms and processes related to the cold-climate (periglacial) and hyperarid environment of Mars and relates the knowledge obtained fromterrestrial research to possible Martian analogue landforms. Among the plethora of landforms related to cold-climate environments and subsurface permafrost on Mars, those features have been investigated in detail that are related to the creep of ice and debris at the Martian dichotomy escarpment and the southern-hemispheric impact basins, especially Hellas Planitia, and which have been described controversially as either glacial or periglacial in nature. Structures related to seasonal freeze-thaw cycles on Mars which are generally known as thermal contraction polygons form a second major focus of this work. Research presented on this topic focuses on the northern hemispheric Utopia Planitia area and the south-polar cap ofMars. Thiswork was carried out on the basis of observational and geomorphometrical analyses by utilizing imaging-sensor and topographic data in order to address questions regarding the history, development, and current state of cold-climate landforms on Mars. This work provides new insights with respect to age, composition, source of debris and ice, and the deformational and degradational history of lobate debris aprons and similar landforms. It is shown that processes which led to creep of debris and ice at the northern hemispheric dichotomy boundary are transitional in nature and are not easily categorized using standard definitions commonly used in terrestrial research. Processes facilitating creep of debris and ice are related to thermokarstic disintegration of permafrost-rich highland terrain coupled with a more recent mantling deposit that is currently disintegrating. These processes are likely the response to cyclic climatic changes in Martian history on a global scale and are related to changes in the configuration of orbital parameters of Mars. Characteristics of recent disintegration processes are observed throughout all study areas in the northern and southern hemisphere and indicate post-emplacement modifications that might have led to rock-glacier formation under cold-climatic conditions. Transitional cryospheric morphologies covering the glacial and periglacial domain appear to exist onMars with debris-ice transport systems containing mostly small amounts of blocky debris and large volumes of ice. Age-determinations for several key regions show that the latest activity phases were approximately 50-100Ma ago. For one area at theMartian dichotomy boundary, much younger ages of <0.1 Ma suggest even geologically recent activity. The south polar cap as part of theMartian cryopshere, is not only seasonally active with respect to sublimation and deposition of carbon dioxide ice but also to seasonal development of thermal contraction cracks, similar to those observed in terrestrial periglacial environments. It is shown for the first time by direct observations that frost cracking does occur seasonally but that formation of ice wedges is unlikely. The configuration of waterand carbon dioxide ice seems to be comparable to terrestrial periglacial landscapes consisting of subsurface permafrost bodies and a surficial seasonally active layer. Guido Grosse, Internet http://www.diss.fu-berlin.de/2007/699/indexe.html