Investigations into the Tectonics of Uranian and Saturnian Icy Satellites

This dissertation reports a range of analyses of tectonic structures on various icy satellites and the implications of these analyses for each satellite’s geologic history. On Miranda, I tested the hypothesis that faults of the Arden Corona boundary and the 340º [degree] Chasma are listric in geometry. A listric fault geometry implies the presence of a subsurface detachment, which likely marked Miranda’s brittle-ductile transition (BDT) at the time of faulting. Results support the hypothesis for the Arden Corona boundary, although not for the 340˚ [degree] Chasma. Using the Arden Corona fault system geometry, the BDT depth, thermal gradient, and heat flux were estimated. Those estimates are consistent with a previously hypothesized heating event associated with an ancient tidal resonance of Miranda with Umbriel and/or Ariel.

On the Saturnian satellites Tethys, Rhea, and Dione, I analyzed normal fault slope geometries to test the hypothesis that faults on icy bodies reflect dip values derived from laboratory deformation experiments in cryogenic H₂O [water] ice. The results show that faults within Ithaca Chasma on Tethys, Avaiki Chasmata on Rhea, and one scarp within Dione’s Wispy Terrain exhibits scarp slopes that are shallower than these values. Analyses of these fault systems indicate that viscous relaxation is the most viable explanation for these shallow slopes. I modeled the potential role of viscous relaxation in creating these shallow fault slopes. The modeling results support the formation of these faults with steep dips, consistent with deformation experiments, followed by their relaxation due to lithospheric heating events.

Finally, I tested for the presence of subtle and/or non-visible fractures within Dione’s Non-Wispy Terrain. A set of statistical analyses of crater rim azimuth data was used to test for polygonal impact craters (PICs) at randomly distributed study locations. The results indicate that PICs are widespread throughout the Non-Wispy Terrain, supporting the hypothesis that fractures are widespread throughout this terrain, despite the lack of visible fractures. These results demonstrate that analysis of crater geometries is a useful tool for identifying and mapping fractures with dimensions below the resolution of available images.