Date

2013

Department or Program

Astronomy

Additional Department or Program (if any)

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Primary Wellesley Thesis Advisor

Wesley Andres Watters

Abstract

Mars, a planet with a tenuous atmosphere and starved of surface water, is a prime location for studying impact craters. Earth’s thick atmosphere stops small craters from forming, and erosion destroys the craters that do. The size range of Martian craters is much greater and craters last much longer than terrestrial craters. The variety of Martian terrain makes it possible to study effects of geology on crater morphology and crater modification, making Mars a much more interesting study location than the Moon. In this project, we investigate the effects of crater size and target geology on crater shape for small (D < 5km), simple impact craters. For example, we see morphometry differences between Vastitas Borealis, sedimentary rocks and volcanics. In addition, we investigate changes in morphology between fresh and modified craters. To study craters on a global scale, we adapted computer programs to generate digital elevation models using stereo images from the HiRISE camera on the Mars Reconnaissance Orbiter and developed new software and algorithms to extract crater rim traces and crater shape statistics automatically. We show that moderate crater age has no apparent effect on rim roundness, and that crater flank elevation profiles in the Northern lowlands have lower power-law decay exponents (αF≤−4) than the global distribution (αF≤−6). We identify a possible crater shape transition at D≈300m to increased rim sharpness. Our results show geologic dependence on crater formation, and can be used to test models of crater formation and modification in the future.

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