Saturn’s iconic rings may be the shattered remains of a long-lost moon, and the same catastrophic event could also explain why the planet is tilted, according to new research.
Results presented at the Lunar and Planetary Science Conference in Texas, which ran from March 10 to 14, suggest that a hypothetical moon called Chrysalis may have ventured too close to Saturn Approximately 100 million years ago, where powerful tidal forces ripped away the icy outer layers of the moon. Some of that debris may have remained in orbit and eventually collided and spread to form the complex ring system we see today.
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“We don’t know if there was a previous ring before this happened,” Jiao told Space.com. But even if there wasn’t, he said, the scenario could still produce an ice-rich ring system consistent with the mass of Saturn’s current rings.
In addition, “it can clearly explain why Saturn’s rings are young,” he said during his presentation.
The new work builds on similar findings from a study 2022 directed by Jack Wisdom at the Massachusetts Institute of Technology, which proposed that Saturn once hosted an additional moon, Chrysalis, which played a crucial role in shaping the planet’s tilt.
The gas giant is tilted about 26.7 degrees and scientists have long suspected that this is related to a gravitational resonance with Neptune – meaning the two planets were once in a sort of orbital rhythm, with Neptune’s repeated gravitational tugs helping to set Saturn’s tilt. In that earlier work, scientists said Chrysalis orbited Saturn for billions of years, helping to maintain that alignment.
But sometime between 100 and 200 million years ago, the moon’s orbit became unstable and a series of gravitational interactions sent Chrysalis into a fatal, brush-by encounter with Saturn. Most of the moon would have been destroyed or fallen on the planet, but a small fraction of the debris remained in orbit, resulting in the raw material for Saturn’s rings, scientists suggest.
Using computer simulations to model the breakup in detail, Jiao’s team found that Saturn’s tidal forces would have preferentially stripped away the moon’s icy mantle, leaving much of its rocky core intact. That distinction naturally explains why Saturn’s rings are composed almost exclusively of water ice, with very little rock, the study notes.
The stripped material was then shaped by gravitational interactions with large moons like Titanwhich could have removed up to 70% of the initial ring’s mass over time. This suggests that the original ring system may have been several times more massive than it is today.
Scientists are still investigating what ultimately happened to Chrysalis’ surviving core and whether remnants of the event may have left traces elsewhere in the Saturn system, such as unusual impact features on icy moons that could perhaps be detected by future spacecraft.
