Simple-To-Complex Crater Transition for the Uranian Satellites Ariel and Miranda

Abstract

The latest decadal survey identified the Uranus system as the highest-priority new target for a NASA Flagship mission. Ariel and Miranda are potential ocean worlds with evidence of resurfacing potentially due to past elevated heat flow. Learning about the geologic histories of these icy moons is important for understanding the potential for life in the outer solar system. Using limited data acquired by the Voyager 2 spacecraft, we explore open questions about the surfaces of Uranian satellites to gain a better understanding of their evolutionary histories. In this work, we update the estimates of Ariel and Miranda's simple-to-complex transition diameters, which have not yet been measured using modern GIS techniques and reprocessed data. The simple-to-complex transition diameter is a value used on many worlds to infer the composition of the surface. For the Uranian satellites, this value was last estimated shortly after the Voyager 2 flyby with a data set of 18 craters. We use reprocessed topography from more than 100 craters to estimate a simple-to-complex transition diameter on Ariel of ∼26 km, consistent with an icy surface composition. We place a lower limit of ∼49 km on the transition diameter for Miranda, where we cannot identify any complex craters. We also estimate the relative and absolute ages of terrains on Ariel and Miranda. Our results agree with recent studies showing that they likely experienced relatively recent (≤1 Gya) resurfacing. Finally, we suggest imaging requirements for the future missions to Uranus to answer outstanding questions about Ariel and Miranda.