MIRANDA’S INVERNESS CORONA: AN EXAMPLE OF AN YIN’S INFLUENCE ON OUTER SOLAR SYSTEM TECTONICS

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. Miranda is the only icy body whose surface is known to contain the enigmatic features called corona—ovoid to trapezoidal areas of deformation. In this work, we seek to constrain potential formation mechanisms for Inverness Corona, the youngest known region on Miranda. To do this, we created the first detailed geologic map of Inverness, enabling the creation of a stratigraphic column of the order of events that formed this region. We find that the bidirectional nature of the extensional features and angular edges of Inverness Corona is reminiscent of triple junctions on Earth, particularly the Afar triple junction. We employed a previously published Digital Elevation Model of the northern region of Inverness Corona to analyze the spacing of features in the region, which we propose to be extensional in origin. From this, we estimate an approximate brittle ice shell thickness of 2.5–3.8 km at the time of the region’s formation, indicating that Miranda’s brittle ice shell may have been relatively thin in the geologically recent past. Here, I present this study as an example of Dr. An Yin’s influence on Outer Solar System tectonics. This study was not done in direct collaboration with An, and he is not an author on this paper, but in one conversation he predicted the outcome years before its completion. As such, it is a great example of An’s intuition and striking ability to link his experience in Earth’s structural geology to the diverse environments in the outer solar system when presented with these unique worlds.