Ariel’s Medial Grooves: Spreading Centers on a Candidate Ocean World

Abstract We present evidence that Ariel's massive chasma-medial groove systems formed via spreading, where internally sourced material ascended and formed new crust. Evidence for this interpretation includes close alignment of offset faults and chasma margins during reconstruction, axial troughs bounded by raised rims, bowed-up chasma floors with marginal valleys, subparallel chasma floor ridges, and relatively young medial groove–bounding terrain. Ariel's medial grooves are among the youngest known Uranian moon geologic features and might be conduits to the interior and the source of NH-bearing species, CO, CO 2 , and other potential internally derived volatiles detected on the surface. While medial grooves are observable in Brownie and Kewpie Chasmata, our results indicate that these features are also present below Voyager 2 Imaging Science System image resolutions in Korrigan, Pixie, and Sylph Chasmata. Close flybys of Ariel with a Uranus orbiter are imperative to uncover the nature of these curious features and to gain insight into this moon's most recent geologic events.