Destruction of a former moon of Saturn may explain the planet’s tilt and young rings

The destruction of a former moon of Saturn could explain the young origin of the planet’s iconic rings as well as its axial tilt, researchers report. Saturn’s rings – thought to have formed a mere ~100 million years ago – are one of the most distinctive planetary features in our solar system. However, how they formed so recently remains poorly understood. What’s more, explanations for the planet’s tilt, or obliquity, and the curious orbits of its largest moon, Titan, have remained elusive. To address this, Jack Wisdom and colleagues use data from the recent Cassini mission and numerical simulations and propose a solution that explains all three of these puzzles. Wisdom et al. argue that the Saturn system experienced a violent event roughly 150 million years ago, when the orbit of a previously existing moon, which they name Chrysalis, was destabilized, causing it to pass close enough to the planet to be ripped apart by tidal forces, forming Saturn’s young rings. According to the authors, this same event could have also caused Titan’s eccentricity to increase to its current high value and explains Saturn’s obliquity. “Wisdom et al. provide a possible mechanism for explaining Saturn’s close proximity to the precession resonance with Neptune and the seemingly young age of its rings,” writes Maryame El Moutamid in a related Perspective. “To further corroborate these claims, further research will need to better define the polar moment of inertia of Saturn and the likelihood of similar events occurring for other planets with rings.”