Saturn is unlikely to have had a tilt during its formation stages
A pre-existing moon likely left Saturn with its bright rings and extreme tilt, according to a new study.
A close encounter with Saturn may have caused the former moon named ‘Chrysalis’ to disintegrate, leading to the formation of the rings, the study hypothesised.
“If we assume that Chrysalis was predominantly made of water ice, like Iapetus (one of Saturn’s existing moons), then this debris could have developed into Saturn’s ring,” the researchers wrote in their study published in Science journal.
Four planets — Jupiter, Saturn, Neptune and Uranus — are known to have rings. Saturn’s rings, composed of water ice particles ranging from microns to tens of metres in size, are the brightest, according to NASA.
Saturn has a tilt of 26.73 degrees, Earth 23.45 degrees and Jupiter 3 degrees.
Saturn is unlikely to have had a tilt during its formation stages, the researchers argued in the study.
Currently, gas giants Neptune, Uranus and Saturn have a substantial tilt, suggesting that this feature did not arise during the formation stages. Jupiter — also a gas giant — is the only exception.
“A variety of theories have been suggested to explain this feature, but none has been convincing,” Jack Wisdom, professor of planetary sciences at the Massachusetts Institute of Technology and lead author of the new study, said in a statement shared with DTE.
Saturn got its tilt due to gravitational interactions with its neighbour Neptune, according to a well-known theory.
But researchers associated with the new study argue that Saturn is no longer under Neptune’s gravitational influence.
Instead, Titan — Saturn’s largest satellite — may have been responsible, suggested observations from NASA’s Cassini spacecraft, which orbited Saturn from 2004-2017.
Titan is migrating from Saturn at about 11 centimetres per year, 100 times faster than previous estimates, a previous study suggested.
Titan’s fast migration caused the planet to tilt further, reducing Nepturn’s gravitational influence on Saturn, it added.
But a crucial piece of information was missing. Saturn’s moment of inertia, which describes how mass is distributed in the planet’s interior, is not unknown.
Saturn’s tilt, the study explained, depends on whether the matter is more packed at its core or toward the surface.
Cassini measured the gravitational field around the entire planet. This, the researchers recognised, can help determine how mass is distributed across the planet.
Saturn was no longer under the grasp of Neptune, pouring water on the Titan migration theory, their analysis showed.
Next, they conducted simulations of the planet’s axis of rotation and how it has changed over time. This revealed that a former moon could be involved, the experts said. Removing the moon gives Saturn its tilt, according to the model.
Chrysalis likely orbited Saturn for several billion years. Roughly 160 million years ago, Chrysalis became unstable and came too close to its planet. This encounter likely pushed the moon away or destroyed it, according to the scientists.
Consequently, it may have helped rescue Saturn from Neptune’s grasp, giving rise to the tilt.
To further corroborate these claims, future research will need to better define the polar moment of inertia of Saturn as well as the likelihood of similar events occurring for other planets with rings, Maryame El Moutamid, senior research associate at Cornell University, wrote in for Science journal.
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