LONG-TERM TECTONIC DEFORMATION OF SATURN’S MOON RHEA, DIONE, AND TETHYS

Saturn’s moons Dione, Rhea, and Tethys are heavily cratered bodies and are overlooked as having tectonized terrains. Some of the most recent terrains on all three moons are ‘wispy terrains’ or chasmata characterized by series of graben and normal fault scarps. Each of these moons also have ancient, sparsely distributed ridges, scarps, and troughs that have survived intense bombardment by impact craters. Differences in orbital distances (Tethys ~4 Saturn radii, Dione ~6 Saturn radii, and Rhea ~9 Saturn radii) and eccentricity (Tethys 0.0001, Dione 0.0022, Rhea 0.00125) may contribute to the varied levels of observed tectonic complexity on each satellite. The presence of two groups of tectonic structures with distinct ages provides an opportunity to assess changes in the stress history of these three moons. From the stress histories we may infer changes in the internal structures of the moons, properties of their ice shells, and potentially heat flux.

Preliminary tidal stress modeling results using SatStressGUI suggest that the wispy terrains on Dione formed due to nonsynchronous rotation. While the pattern of wispy terrains on Rhea and Tethys look similar, Tethys’ wispy terrains have been attributed to the formation of the large basin Odysseus, however the fracture patterns across Rhea and Tethys are similar to those on Dione. Characterization of the types of tectonic structures across these three moons and stress modeling is ongoing and will result in a better understanding the stress mechanisms that may have formed the recent and ancient troughs and scarps across these moons. We present our characterizations of the morphology of the recent and ancient tectonic structures on each of these three moons and present preliminary tidal stress models using SatStressGUI to assess first order fits with global scale stress fields.