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Abstract
Mercury, the smallest planet in the Solar System and closest planet to the Sun, has undergone global contraction, which is a process causing the planet to shrink due to its long, sustained cooling. This has led to the formation of thousands of shortening landforms distributed across Mercury’s surface. These positive-relief, surface-breaking landforms are caused by the folding over thrust faults. Traditionally, Mercury’s shortening landforms have been classified into one of three categories: “lobate scarps”, “wrinkle ridges”, and “high-relief ridges”. In this dissertation, these categories are assessed through multiple statistical analyses. The subsurface fault geometry is then modeled for a large sample size of Mercury’s shortening landforms. These statistical and modeling efforts both inform a new assessment of Mercury’s global contractional strain. Finally, Mercury’s current orbit and rotation is assessed for its influence on the observed systemic thrust fault orientations. Through this work, Mercury’s shortening landforms are found to exist along a morphological spectrum between “lobate scarp” and “wrinkle ridge” designations, suggesting that the morphology of Mercury’s shortening landforms does not support these categories. Mercury’s shortening landforms are also shown to host a wide range of thrust system geometries that include single-listric faults, imbricate stacks, and push-up structures. This data set is then used to establish globally observed ranges of geometric fault parameters which are then used to inform strain calculations. Using multiple thrust fault data sets, Mercury’s radial contraction is estimated to be multiple kilometers over a wide range of plausible physical parameters. The systematic orientations of Mercury’s thrust faults also seem to be influenced by the stresses caused by the planet’s current orbital configuration overlain onto global contraction. The collection of research presented in this dissertation provides valuable insight into Mercury’s tectonic character.