Early tidal despinning history recorded in the tectonics of Oz Terra, Charon

Abstract

Abstract Records of early geologic and thermal evolution after planetary accretion are rarely preserved on icy moons in the Solar System. Charon’s ~ 4.0 Ga surface age suggests the potential preservation of landforms induced from early orbital evolution. Here we show that despinning-induced stress inferred from compressive tectonic features explains latitudinal variations in the orientations and types of tectonic features in Charon’s northern highland, Oz Terra. In addition to global extensional features, we identify north-trending arcuate ranges in Oz Terra, interpreted as compressional in origin. Using an elastic dislocation model, we infer the geometry and kinematics of two thrust faults by fitting the observed tectonically induced topography. The inferred geometry yields a lower bound of 30–36 km for the elastic ice shell thickness at the time. The thrusts accommodate ~ 1 % east-west compressive strain in the equatorial area. The corresponding flattening change suggests an initial rotation period of ~ 14.3 h for Charon. The modeled stress patterns also account for the east-west extensional features. Our work suggests that Charon’s surface presents an example that records the planetary despinning history, which predates the proposed global extension and cryovolcanism on Charon. The coevolution of despinning and global contraction favors a cold start for Charon, offering insights into the early thermal evolution of icy satellites in the outer Solar System.