Cold-Climate Landforms on Mars
Gasselt, Stephan van

HaupttitelCold-Climate Landforms on Mars
TitelvarianteKaltklimatische Oberflächenformen des Mars
AutorGasselt, Stephan van
Geburtsort: Meerbusch, Deutschland
GutachterGerhard Neukum
weitere GutachterRalf Jaumann
Margot Böse, Christoph Heubeck, Claudio Rosenberg
Freie SchlagwörterMars, Remote Sensing, Cold-Climate Landforms, Periglacial, Permafrost
DDC550 Geowissenschaften
ZusammenfassungThis 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 from terrestrial 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 of Mars. This work 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 on Mars 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 50-100 Ma ago. For one area at the Martian dichotomy boundary, much younger ages of <0.1 Ma suggest even geologically recent activity. The south polar cap as part of the Martian 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 water- and carbon dioxide ice seems to be comparable to terrestrial periglacial landscapes consisting of subsurface permafrost bodies and a surficial seasonally active layer.
Fachbereich/EinrichtungFB Geowissenschaften
Anmerkungen des AutorsGleichzeitig erschienen im Shaker Verlag, ISBN 978-3-8322-6660-8
Tag der Disputation16.02.2007
Erstellt am21.10.2007 - 00:00:00
Letzte Änderung19.02.2010 - 14:03:29
Alte Darwin URLhttp://www.diss.fu-berlin.de/2007/699/
Statische URLhttp://www.diss.fu-berlin.de/diss/receive/FUDISS_thesis_000000003198