CONSTRAINING OCEAN AND ICE SHELL THICKNESS ON ARIEL USING GEOLOGIC STRUCTURE MAPPING AND STRESS MODELING

The Voyager 2 flyby of the Uranian satellite, Ariel, provided the first glimpse of a geologically young surface (~1 Ga) with evidence of possible tectonic and cryovolcanic resurfacing. Subsequent studies suggest Ariel shows the presence of cryovolcanic flows, as well as chemical species of possible endogenic origin (1-3). Our research investigates the possible cause of the recent episode of geologic deformation by constraining the interior structure of Ariel, including the thickness of its ice shell and subsurface ocean. We modelled the stress using SatStress and then compared its predictions to geologic structure maps. Our modeling suggests a thin (≤ 30 km) ice shell during a period when Ariel’s eccentricity was ~0.045. The deviation in eccentricity is necessary to generate sufficient tidal stress to break Ariel’s ice leading to geological resurfacing. Our mapping results further support an alignment between Ariel’s linear grabens and the predicted orientation of stress due to eccentricity tides across the surface. A thin ice shell in the geologically recent past is consistent with Ariel having experienced an intense heat pulse from tidal heating from eccentricity tides that melted the icy interior. Our results agree with dynamical studies which predict Ariel’s eccentricity was excited to values ~0.045 due to complex orbital evolution during a mean-motion resonance with Umbriel (4-5).

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