Charon: A brief history of tides

TL;DR

This paper investigates whether tidal stresses caused fractures on Charon, concluding that tidal forces likely did not play a significant role in its geological features, with other processes probably responsible.

Contribution

It provides an analysis of tidal stress effects on Charon's fractures, suggesting tidal forces were not the primary cause of observed geological features.

Findings

No correlation between fracture orientations and tidal stress predictions

Charon's orbit likely circularized before surface freezing

Tidal stresses alone probably insufficient to cause fractures

Abstract

In 2015, the New Horizons spacecraft flew past Pluto and its moon Charon, providing the first clear look at the surface of Charon. New Horizons images revealed an ancient surface, a large, intricate canyon system, and many fractures, among other geologic features. Here, we assess whether tidal stresses played a significant role in the formation of tensile fractures on Charon. Although presently in a circular orbit, most scenarios for the orbital evolution of Charon include an eccentric orbit for some period of time and possibly an internal ocean. Past work has shown that these conditions could have generated stresses comparable in magnitude to other tidally fractured moons, such as Europa and Enceladus. However, we find no correlation between observed fracture orientations and those predicted to form due to eccentricity-driven tidal stress. It thus seems more likely that the orbit of Charon circularized before its ocean froze, and that either tidal stresses alone were insufficient to fracture the surface or subsequent resurfacing remove these ancient fractures.