First modification: 16/09/2022 – 00:44Last modification: 16/09/2022 – 00:42
Washington (AFP) – Among all the planets in our solar system, Saturn is certainly the one that most attracts the imagination, thanks to its immense rings.
But there is no consensus among experts about his origin or training, not even about his age.
However, a study published Thursday in the prestigious journal Science attempts to provide an answer to that long-standing question.
According to this research, a Moon that got too close to Saturn was broken up 100 million years ago, and its remains were then put into orbit around the planet.
“Saturn’s rings were discovered by Galileo about 400 years ago, and are one of the most interesting objects in the solar system to observe through a small telescope,” said Jack Wisdom, author of the study.
“It is satisfying to have found a plausible explanation” for his formation, this professor of planetary sciences at the Massachusetts Institute of Technology (MIT) confided to AFP.
Saturn, the sixth planet around the Sun, was formed 4.5 billion years ago, at the origins of the solar system.
But a few decades ago, scientists claimed that Saturn’s rings appeared much later: about 100 million years ago.
That hypothesis was reinforced by observations from the Cassini probe, launched in 1997 and retired in 2017.
“But since no one was able to determine how these rings only appeared 100 million years ago, some questioned the reasoning,” explains Wisdom.
Wisdom and his colleagues then built a complex model that allows not only to explain its recent appearance, but also to understand the planet’s tilt.
Saturn’s axis of rotation is tilted 26.7° from its vertical. And being this planet a gas giant, it could be expected that the process of accumulation of matter that led to its formation would have prevented that tilt.
gravitational forces
The researchers, who through complex mathematical models, reached a recent discovery: Titan, the largest satellite of Saturn (of the more than 80 it has) moves away at a rate of 11 centimeters per year.
That motion slowly changed the frequency at which Saturn’s axis of rotation makes a complete turn around the vertical, a bit like a tilted top.
An important detail since about 1,000 million years ago, this frequency came into synchrony with the frequency of Neptune’s orbit; a powerful mechanism that caused Saturn to tilt up to 36°.
However, the researchers found that this synchronization between Saturn and Neptune (called resonance) was no longer exact and only a powerful event could disrupt it.
They hypothesized that a chaotic orbiting Moon got too close to Saturn, until contradictory gravitational forces caused it to break apart.
“It broke into several pieces, and these pieces, also dislocated, gradually formed rings,” explains Wisdom.
The influence of Titan, which continued to recede, eventually reduced Saturn’s tilt to the level that can be seen today.
Chrysalis
Wisdom named the moon Chrysalis (Chrysalis), comparing the appearance of Saturn’s rings to a butterfly emerging from a cocoon.
Scientists thought that Chrysalis was slightly smaller than our Moon, and about the size of another satellite of Saturn, Japet, which is made almost entirely of ice.
“It is then plausible to hypothesize that Chrysalis is also made of frozen water, which is needed to create the rings,” says the professor.
Do you think you have solved the mystery of Saturn’s rings?
“We have delivered a good contribution,” he replies, before adding that the system still contains “many mysteries.”
© 2022 AFP