Saturn’s rings may have been formed by a missing moon that crashed into the planet around 160 million years ago, scientists believe.
The absent moon, called Chrysalis, could also explain why the planet tilts slightly in its rotation.
Chrysalis used to orbit Saturn for several billion years before crashing into the planet and breaking apart.
Researchers from the Massachusetts Institute of Technology (MIT) said it could also explain the origin of Saturn’s famous ice rings, which are estimated to be around 100 million years old, much younger than the planet itself.
These rings of ice that orbit the planet’s equator clearly show that Saturn is rotating at a tilt of 26.7 degrees, and astronomers have long thought that this tilt stems from gravitational interactions with its neighbor, Neptune.
The belted giant precedes, or wobbles, like a spinning top at roughly the same rate as Neptune’s orbit, albeit slightly out of sync.
Publish your work in the journal Sciencethe MIT team said Chrysalis, what would have been Saturn’s 84th moon, tugged and tugged on its parent in a way that kept its tilt, or obliquity, in resonance with Neptune.
But the loss of its gravitational influence since its destruction means Saturn and Neptune have gone out of sync.
“Just like a butterfly’s chrysalis, this satellite was dormant for a long time and suddenly became active and the rings emerged,” said MIT Professor Jack Wisdom, lead author of the study.
In the early 2000s, scientists suggested that Saturn’s tilted axis resulted from the planet being trapped in a resonance, or gravitational association, with Neptune.
But observations taken by NASA’s Cassini spacecraft, which orbited Saturn from 2004 to 2017, revealed that Titan, Saturn’s largest satellite, was moving away from Saturn faster than expected, at a rate of about 11 centimeters per year.
Titan’s rapid migration and gravitational pull led scientists to conclude that the moon was likely responsible for tilting and keeping Saturn in resonance with Neptune.
But this explanation is based on a major unknown: Saturn’s moment of inertia, which corresponds to the distribution of mass inside the planet.
Saturn’s tilt could behave differently depending on whether matter is more concentrated at its core or toward the surface.
“To make progress on the problem, we had to figure out Saturn’s moment of inertia,” Wisdom said.
In their new study, Wisdom and his colleagues sought to determine Saturn’s moment of inertia using some of the latest observations taken by Cassini during its grand finale, a phase of the mission during which the spacecraft performed a extremely close approach to accurately map gravitational gravity. field around the entire planet.
The gravitational field can be used to determine the distribution of mass in the planet.
Wisdom and his colleagues modeled Saturn’s interior and identified a mass distribution that matched the gravitational field observed by Cassini.
Surprisingly, they discovered that this newly identified moment of inertia placed Saturn near but just outside of resonance with Neptune. The planets may have been synchronized but are no longer.
“Then we went looking for ways to get Saturn out of Neptune’s resonance,” Wisdom said.