In addition, there are unresolved questions about the age of these satellites, with some suspecting that they formed more recently (like Saturn's rings, which are a few hundred million years old).

To address these questions, an international team of astronomers created a series of high-resolution simulations coupled with improved estimates of trans-Neptunian object (TNO) populations.

This allowed them to construct a chronology of impacts for Saturn's most heavily cratered regular satellites—Mimas, Enceladus, Tethys, Dione, and Rhea. This established age limits of 4.1 and 4.4 billion years for all five, with the two innermost moons appearing more youthful than the outer three. These results could have significant implications for our understanding of the formation and tidal evolution of moons in the outer solar system.

The research was led by Emily Wai Wong, a researcher with the Earth-Life Science Institute (ELSI) at the Tokyo Institute of Technology. She was joined by Ramon Brasser, an associate professor at the ELSI and the Origins Research Institute at the Research Center for Astronomy and Earth Sciences (ORI-RCAES), Stephanie C. Werner, the deputy director of the Center for Planetary Habitability (PHAB) at the University of Oslo, and lead research scientist Michelle R. Kirchoff of the Southwest Research Institute (SwRI).

Their paper, "Saturn's ancient regular satellites," appeared in the journal Icarus.