THE GEOLOGIC HISTORY OF MIRANDA’S INVERNESS CORONA

In the images returned by Voyager 2, Miranda, a mid-sized icy moon of Uranus, has a surface made up of a patchwork of geologically old and young surface regions. The lack of impact structures in some regions suggests a period of relatively recent geologic activity (<1 Ga). Fractures, ridges, scarps, and a relative dearth of craters larger than about 10 km diameter, likewise point to a history of significant tectonic resurfacing. This resurfacing is also evidenced by the coronae--three large (>200 km in diameter) ovoid to rectangular structures on Miranda’s surface. Previous work on the coronae hypothesize that they formed through extensional tilt-block style tectonism and/or cryovolcanic processes. Here we seek to constrain potential formation mechanisms for Inverness Corona, the youngest corona on Miranda. In order to do so, we have created a detailed geologic map of the Inverness Corona region. The geologic units in our detailed geologic map—crater material, crater ejecta material, scarp material, cratered plains material, rounded ridge material, bright corona material, inner corona material, outer corona material, and chasma material—include units based on the relative brightness of the terrain within the corona and the crater density and morphology outside of the corona. We identify several linear features that are too small to be mapped as units at this scale—scarps, troughs, and ridges. We also map small (<2 km diameter) craters as point features. Following the completion of the geologic map of Inverness Corona, we have started investigating the history of deformation in the region. Initial observations of the stratigraphy of the geologic units show that, as expected, the cratered plains material is older than the corona material. Interestingly, at least some of the chasma material and scarp formation post-dates the formation of the outer corona material, evidenced by cross-cutting relationships in the northern part of the corona. Scarps and scarp material within the corona and outside the corona in the cratered plains appear to run sub-parallel to the edges of the corona. In order to aid with the deformational history analysis, we will investigate feature topography using newly completed digital elevation models (DEMs) of the region.