TECTONIC RESURFACING ON URANUS’S MOONS ARIEL AND MIRANDA

Uranus’s icy satellites Ariel and Miranda, both display surprisingly young surfaces that suggest a period of recent resurfacing activity. The young surface ages of these moons is implied by a dearth of large craters (>10 km diameter) and evidence for significant tectonic activity in the form of fractures, ridges, and scarps. Here we constrain the potential tectonic formation of these structures through numerical stress modeling and analogue models. In order to determine if the driving stresses to create the observed structural features are tidally controlled, we use SatStressGUI to calculate the magnitude and orientation of the resultant stresses. We perform a range of simulations that vary ice shell and ocean thicknesses, and orbital eccentricities to determine the range of magnitudes and orientations of potential stresses. We then compare the resultant stresses to mapped features on the surface to determine if there is a correlation. In order to physically simulate chasmata formation, we develop a two-layer analogue experiment to simulate an extensional environment on Ariel. We then compare the resulting morphology of the graben produced to observations of the tectonic structures. The analogue model consists of a ductile, lower viscosity layer underlying a Coulomb-material brittle layer. This modelling serves to constrain the brittle and ductile thicknesses used in the analogue modelling aspect of this work. These two techniques combined can aid in determining if the moons had larger eccentricities in the past that could have resulted in larger stresses. We are also able constrain the depth to, and thickness of, any potential subsurface liquid water layer.