Evidence of the slowing of Charon's spin period (despinning) is recorded in tectonic features on the surface of Pluto's icy moon, according to a modeling study published in Nature Communications. The findings offer insights into the early thermal evolution of Charon and other icy satellites in the outer solar system.
Objects across the solar system are thought to undergo a process called despinning, in which tidal forces may slow a body's rotation rate, altering its shape and temperature. Although the mechanism has long been theorized to occur on Charon, clear geological evidence has been lacking. Charon is a promising candidate for such evidence because its surface is about 4 billion years old and has experienced relatively limited resurfacing compared with other icy satellites.
Hanzhang Chen and colleagues examined variations in the orientations and types of tectonic features in mountain ranges in a region called Oz Terra, in Charon's northern hemisphere. These features extend more than 200 km (124 miles) and display asymmetric slopes consistent with compression rather than extension. Modeling indicates the presence of an ice shell at least 30–36 km thick at the time of formation and suggests that the crust near the equator became approximately 1% shorter during this time, with the compression absorbed along existing fault lines and creating the observed ridges.
The modeling leads the authors to estimate that Charon's early rotation period was approximately 14.3 hours, notably faster than its present tidally locked state of around 153.3 hours. This provides evidence supporting a gradual slowing, or despinning, of its rotation.
These findings suggest that Charon may have begun its evolution in a relatively cold state, forming a thick, rigid ice shell early on. While uncertainties remain in modeling assumptions and stress estimates, the study provides a rare geological record of rotational evolution, with implications for understanding the thermal and orbital histories of other icy satellites.
Publication details
Hanzhang Chen et al, Early tidal despinning history recorded in the tectonics of Oz Terra, Charon, Nature Communications (2026). DOI: 10.1038/s41467-026-75069-7
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Citation: The spin of Pluto's moon, Charon, may be slowing down (2026, July 14) retrieved 14 July 2026 from https://phys.org/news/2026-07-pluto-moon-charon.html
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