THE TECTONIC ORIGIN OF DEPOSITS IN GALE CRATER, MARS

As much as Ron Greeley was a teacher at heart, the greatest lessons he had to share he taught by his own example. Perhaps the most practical of those lessons was that exploration is led by curiosity, honesty, and the pursuit of answers to simple questions. In light of that lesson and in that spirit, we ask, “What role did tectonics play in shaping Mt. Sharp, the large mound of deposits in Gale Crater?” Presently, the mound is thought to represent a thick sequence of layered, largely sedimentary rock that formed from deposited materials that filled the crater and were subsequently eroded. The question of tectonics seems to have escaped significant scrutiny thus far, yet it is important to consider. Most mountains on Earth are constructed through tectonism. Most cases of mass erosion on Earth are driven by tectonic uplift. Although Mars appears not to have had plate tectonics, it does not mean that Mars did not experience significant tectonic processes. In order to address this question, we have examined orbiter imaging data from the Thermal Emission Imaging System (THEMIS), the Context Imager (CTX) and the High Resolustion Imaging Science Experiment (HiRISE), stereo imaging from HiRISE, and Mars Orbiter Laser Altimeter (MOLA) data. Our geomorphological analysis shows that most of Mt. Sharp is replete with complex joint systems and collapse features. We also observe thrust faults, tear faults, normal faults and drag folds. The major structural features on Mt. Sharp have trends matching observed regional features, most notably the crustal dichotomy. From these and other observations we conclude that Mt. Sharp was formed principally through tectonic uplift, which was likely aided by reactivation of subsurface structure of the crater’s central peak. Most, if not all, of Mt. Sharp is composed of rocks that had previously resided beneath the floor of Gale Crater, meaning they are significantly older than the Hesperian age they are presently assigned. This has major implications for how clay and sulfate materials examined by the Curiosity Rover will be interpreted and how those materials fit into the overall history of Mars.