CONSTRAINING OCEAN AND ICE SHELL THICKNESS ON MIRANDA FROM SURFACE GEOLOGICAL STRUCTURES AND STRESS MODELING

Images from the Voyager 2 mission revealed the small (R ~ 235 km) Uranian satellite Miranda to be a very complex and dynamic world. This is exemplified by unexpected signs of geologic activity, including an extensive fault system and the mysterious coronae, smooth square or ovoid regions of radial ridge-like structures. This has led to speculation that Miranda may been active within the geologically recent past and could host a subsurface liquid water ocean. In this work, we aim to constrain the thickness ranges for the ice shell and potential ocean on Miranda. Here we present the results of our geological mapping of craters, ridges, and faults on the surface. We also present the results of our comparison of the location and orientation of these features on Miranda’s surface to stress models for the icy satellite. These stress models predict where, when, and in what orientation in space the maximum tensile or compressive stress occurs on the surface of the icy satellite during its orbit around Uranus. The stress models are created using the software, SatStressGUI. In addition to diurnal tidal stress, we also use SatStressGUI to model nonsynchronous rotation, true polar wander and obliquity to determine the stress configuration and how it matches the surface geology. These stress models have been used to determine that some sources of stress, such as eccentricity, are not enough to create the features observed with the modern orbital parameters and suggested ice shell thicknesses. This suggests Miranda experienced enhanced geologic stresses in the past, possibly related to a thicker ocean, differing orbital parameters, and/or motions of the ice shell.