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Grid-mapping the northern plains of Mars : study of periglacial landforms in Utopia Planitia

A Sejourne, MCF,F Costard DR

Scientific interests

The region of Utopia Planitia in the mid-latitudes of Mars shows different landforms that are thought to be periglacial and indicate the presence of ground-ice. The landforms comprise flat-floored depressions with scalloped shapes (Costard and Kargel, 1995; Morgenstern et al., 2007; Lefort et al., 2009; Séjourné et al., 2009; Soare et al., 2005; Soare et al., 2007; Ulrich et al., 2010); spatially-associated polygonal patterned-ground (Levy et al., 2009; Lefort et al., 2009; Mellon, 1997; Morgenstern et al., 2007; Pechmann, 1980; Seibert and Kargel, 2001); pingo-like mounds (Burr et al., 2009; Dundas et al., 2008; Soare et al., 2005); and polygon-junctions pits (Morgenstern et al., 2007; Séjourné et al. 2010; Wan Bun Tseung and Soare 2006). The scalloped depressions are thought to be the result of ground-ice degradation (Costard and Kargel, 1995; Morgenstern et al., 2007; Lefort et al., 2009; Séjourné et al., 2009; Soare et al., 2005; Soare et al., 2007). There is an ongoing debate regarding the formation processes of these Martian depressions, whether they are formed by sublimation or thawing. The polygonal patterned-grounds have shape and size consistent with thermal-contraction cracking of an ice-cemented regolith (Levy et al., 2009; Mellon, 1997; Morgenstern et al., 2007).

These landforms ask numerous questions about processes of formation : i) What are the processes and climatic conditions during formation of this landforms? Was there a climatic change on Mars? ii) What is the origin of the ground ice, if the processes implied thawing/sublimation of ground ice?

Figure : Scalloped depressions with polygonal patterned ground in Utopia Planitia, Mars. Credit: NASA/JPL/University of Arizona

Purposes

The goal of this thesis is to perform a comparative study between scalloped depressions on Mars and periglacial landforms on Earth. The first part consists of a geomorphological study of the Western part of Utopia Planitia (35°-50°N and 80°-110°W). The second part is the study of periglacial regions of Earth, particularly the study of thermokarst processes. All the results will allow to propose a schematic model of formation of scalloped depressions.

The study will be performed during a thesis (2009-2011 Antoine Séjourné) with scientific collaborations with the Dawson College in Montreal (Professor Richard Soare) and with the Permafrost Institute of the Russian Academy of Sciences in Yakutsk (Siberia) for field study in Canada and Central Yakutia.

Geomorphological study of Mars

The study of all landforms at the Western part of Utopia Planitia will use the new high resolution imagery HiRISE (High Resolution Imaging Science Experiment) on board Mars Reconnaissance Orbiter (MRO) as well as HRSC camera from MarsExpress mission. The photo-interpretation will allow to characterize all landforms at the surface with the highest resolution on Mars (25 cm/pixel). Furthermore, CTX images (Context Camera of MRO) will be used to have a global view of the region (6 m/pixel) and THEMIS IR images of Mars Odyssey (100 m/pixel) to compare the thermal inertia of different landforms. The altimetric data of MOLA (Mars Orbiter Laser Altimeter of Mars Global Surveyor) directly extracted from satellite tracks (From the Orsay Planetary Library) and a new Digital Elevation Model from HiRISE stereo images will allow to know precisely the geometry and inner topography of the scalloped depressions. The goal is to produce a systematic classification of all landforms in Western Utopia Planitia necessary to formulate hypotheses of formation. This will allow to know whether the formation of scalloped terrains is by thawing of by sublimation.

Comparative study of Earth: Thermokarst processes

The thermokarst lakes are the result of the ground subsidence following the localized thawing of excess-ice (French, 2007; Soloviev, 1973). The term thermokarst denotes the processes and landforms associated with degradation, of excess-ice in permafrost (amount of ice exceeds the natural pore water content in a non-frozen state) (Washburn, 1973). The development of thermokarst results from the localized disruption of the thermal equilibrium of the permafrost consequently of an increase in surface temperature and a deepening of the active-layer (Murton et al., 2001; Soloviev, 1973).

The second part consists of a study of periglacial region on Earth. The classification of Martian landforms will be compared with terrestrial landforms. Terrestrial periglacial landscape will be studied with a combination of satellite SPOT images (20 to 10 m/pixel) and field works in Canada (cooperation with R. Soare) and in Siberia (cooperation with Permafrost Institute, Yakutsk). Special attention will be paid to the differences between Martian and terrestrial landforms. Notably, to know if liquid water has been implied in the formation of scalloped terrains or if they are the result of sublimation. That approach requires a complete comparative study with terrestrial thermokarst depressions as well as a close cooperation with climatic model (GCM from LMD Laboratory, France). This study of periglacial environment on Earth is critical to understand the main mechanisms of formation of scalloped terrains.

Grid map of ice-related landforms in Utopia Planitia https://transfert.u-psud.fr/34cmi





IDES Université Paris-Sud 11 CNRS Faculté des Sciences
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