Charon's Rotation Slowed Over Time, New Study Shows

Researchers led by Hanzhang Chen of ETH Zurich and UCLA published new findings in Nature Communications that Charon’s rotation period has decreased dramatically, from an early value of roughly 14.3 hours to the current tidally‑locked period of about 153.3 hours.

Analysis of tectonic features in the northern Oz Terra region revealed compressional ridges inconsistent with previous extension models. Computer modeling indicates the moon’s ice shell was initially 30‑36 km thick and that the equatorial crust shortened by about 1%, creating the observed ridges. These observations, supported by data from NASA’s New Horizons flyby, suggest Charon began with a cold start and that its surface preserves a record of planetary despinning, offering new insight into the thermal evolution of icy satellites in the outer Solar System.