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10 - Debris flows in Greenland and on Mars
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- By François Costard, UMR 8148 IDES, Université Paris-Sud, François Forget, Laboratory for Dynamic Meteorology, Paris, Vincent Jomelli, CNRS UMR 8591, Laboratoire de Géographie Physique, Meudon, Nicolas Mangold, UMR 8148 IDES, Université Paris-Sud, Jean-Pierre Peulvast, UMR 8148 IDES, Université Paris-Sud
- Edited by Mary Chapman
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- Book:
- The Geology of Mars
- Published online:
- 18 September 2009
- Print publication:
- 17 May 2007, pp 265-278
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- Chapter
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Summary
Introduction: Martian gullies and terrestrial debris flows
The observation of small gullies on Mars was one of the more unexpected discoveries of the Mars Observer Camera (MOC) aboard the Mars Global Surveyor (MGS) spacecraft (Malin and Edgett, 2000). Gullies are the flutes and narrow troughs formed by the debris flows process and not the process itself. They mostly occur in a latitudinal band higher than 30°. The upper parts of the slopes (mostly south facing slopes in the southern hemisphere) exhibit alcoves, with generally broad and deep channels. They are characterized by their distinct V-shaped channels with well-defined levees. Individual channels exhibit low sinuosity and deep erosion down to the fans that bury the lower parts of the crater walls (Figure 10.1). These debris fans correspond to one or several lobes.
The characteristics of these gullies suggest that they were formed by flowing water mixed with soil and rocks transported by these flows. They appeared to be surprisingly young, as if they had formed in the last few million years or even more recently. In their initial analysis, the MGS Camera investigators Mike Malin and Ken Edgett (2000) proposed a scenario involving ground water seepage from a sub-surface liquid water reservoir located a few hundred meters or less below the surface. However, the process capable of maintaining such a shallow aquifer at temperatures above the freezing point of water remains unclear.