THE ROLE OF ROCK FRACTURE IN MARTIAN LANDSCAPE EVOLUTION

The 27 km journey across the floor of Gale Crater and up the footslopes of the 5 km high Mt. Sharp that occupies the center of the crater has revealed a rich stratigraphic history of fluvial, lacustrine, and aeolian sediments. These deposits were buried, lithified, altered by diagenesis, and subject to billions of years of wind driven erosion which etched out the strength variability of the bedrock, leading, in particular, to resistant sandstone caps on underlying mudstones forming isolated buttes and steep retreating bluffs. Wind has also shaped less strongly lithified bedrock into oriented rounded hilltops. All of the bedrock is broken. Many processes are likely at work to break the rocks including impacts, differential heating, periglacial processes, wetting and drying, and, perhaps topographic-induced stresses. Breaking the rocks enables cliff retreat and shedding of blocks on rounded hillslopes. This breaking, however, also becomes an erosional rate limiting step on retreating bluffs and scarps because the loosen blocks form a slope mantle reducing wind erosion. The intention of this talk is to invite a mechanistic analysis of the relative roles various rock break processes may play and to ask what measurements “in the field” with the Curiosity rover could be done to test proposed mechanisms.