EXPLORING DIONE'S GEOPHYSICAL EVOLUTION

Saturn’s fourth largest moon Dione preserves one of the most heavily tectonized surfaces in the Saturn system. Only Enceladus and Titan have experienced greater tectonic modification. Dione’s surface preserves a complex geophysical history, which can be used to assess changes in Dione’s tectonic activity at two periods in time. Late-stage tectonic activity is preserved in the recent wispy terrains of Dione’s trailing hemisphere, dominated by normal fault scarps and graben. Evidence for the early-stage tectonic activity is recorded in ancient ridges, troughs, and scarps that occur less frequently, and are distributed globally outside of the wispy terrains.

Two distinct stages of tectonism allow for a first order temporal assessment of changes in global-stress mechanisms and geophysical history. Here we model relevant global stress mechanisms for the populations of both early- and late-stage tectonism. Preliminary models suggest the wispy terrains formed as a result of nonsynchronous rotation. The implications of nonsynchronous rotation at the time of wispy terrain formation suggest that a global ocean was present at the time of formation. We will present global models of ancient tectonic structures to determine whether the early stress history is consistent with late-stage tectonic activity. We will also present minimum inferred brittle ice shell thicknesses modeled from available topographic data at both at early- and late-stage structures. Assessing whether Dione has experienced changes in a global stress field and its internal structure will reveal a glimpse of Dione’s geophysical evolution.