How to explain Saturn's unique tilt and the youth of its rings? A recent hypothesis puts forward the idea of a cataclysmic event in the past of its largest moon, Titan.
Cassini's measurements indicated that the distribution of mass inside Saturn differs slightly from previous models. This discovery changes the calculation of its moment of inertia, pulling the planet out of a long-term gravitational resonance with Neptune's orbit. Without this stabilizing interaction, Saturn would have developed a marked inclination.
Artist's representation of Titan's landscape with a hazy atmosphere.
Scientists have also considered the existence of an icy moon, now gone, named Chrysalis. According to numerical simulations, this moon would have been perturbed by Titan before moving dangerously close to Saturn. Approximately 100 million years ago, the gas giant's tidal forces would then have torn it apart. Its debris would now make up the rings, while the gravitational interaction with Chrysalis would have altered Titan's orbit.
Nevertheless, modeling has shown a more likely alternative scenario: Chrysalis collided more frequently with Titan itself, rather than being torn apart near Saturn. This merger between Chrysalis and a proto-Titan would then have reshaped the moon's surface, which would explain its low number of craters as well as the genesis of its dense atmosphere. The cataclysmic event would also have released materials from Titan's internal layers.
Following this impact, Titan's orbit, altered, would have both widened and elongated. This transformation would in turn have affected other satellites, such as Hyperion, whose orbital resonance with Titan would date precisely from this period. Hyperion might even be a relic of this collision, having aggregated from ejected fragments, according to work published in the
Planetary Science Journal.
The disturbances generated by this episode would also have marked Iapetus, giving it its highly inclined orbit. Furthermore, collisions between inner moons would have released large amounts of icy particles, thus contributing to the formation of Saturn's rings. The simulations reinforce this scenario.
If this hypothesis matches current observations, it requires confirmation. NASA's Dragonfly mission, whose launch is planned for 2028, could search for clues about the youth of Titan's surface, possibly providing tangible evidence of these events. Researchers hope to more accurately reconstruct the history of the Saturnian system in this way.
Gravitational resonance
Gravitational resonance occurs when two celestial bodies have orbits whose periods are in a simple ratio, for example 4:3 or 2:1. This relationship can either stabilize or destabilize their trajectories over long time scales, influencing their movement around a more massive object like a planet.
In the Solar System, such resonances are observed between several moons and planets. Jupiter's satellites provide an example, with resonances that preserve the regularity of their orbits. These interactions can protect bodies from collisions or, conversely, lead them toward encounters.
For Saturn, the resonance between Titan and Hyperion constitutes a notable case. Their orbital lock implies that for four revolutions of Titan around Saturn, Hyperion completes exactly three.
Gravitational resonance thus represents a valuable tool for modeling the history of planetary systems. It allows astronomers to trace orbital changes over millions of years, providing clues about ancient episodes that shaped the worlds we observe today.