The image of the planet Saturn taken by NASA in 2008 (photo illustration).
SPACE – While Saturn’s rings are beautiful to look at, they are also a huge headache for scientists trying to study them. When and how did they manage to form around this gas giant planet? A new study published in the journal Science on Thursday, September 15, provides some answers.
“Saturn’s rings were discovered by Galileo about 400 years ago, and they are one of the most interesting things to observe in the solar system”, enthusiastically launched Jack Wisdom, a specialist in planetary dynamics at the Massachusetts Institute of Technology (MIT) and lead author of the study. With his team, he developed a model, which shows that the famous rings recently appeared in our solar system, and even recently on an astronomical scale.
Because that’s one of the big questions scientists are asking about Saturn: Did these countless chunks of ice form billions of years ago – and therefore as old as the solar system itself? the same – or about 100 million years ago? This second hypothesis gained weight in the scientific community after the observations of the Cassini probe in 2017.
The spacecraft actually discovered that the rings were exposed to a shower of coal dust from the solar system, which would have darkened them over time. But they are not “dirty” enough to be 4.5 billion years old. According to Jack Wisdom, these relatively intact rings should logically be young. But how do you explain what created the rings, especially so late in the history of the solar system?
Scientists are working on Saturn’s tilt
By looking at a completely different subject, scientists have found an explanation for the recent formation of these rings. In fact they were originally working on the astonishing inclination of Saturn.
Saturn’s axis of rotation is actually inclined at 26.7° from the vertical. But Saturn being a gas giant, the accretion process that led to its formation should have left it perpendicular to the plane of its orbit.
To find an explanation, researchers started with a new discovery: Titan, the largest satellite of Saturn, is gradually moving away from it… According to researchers, this movement is gradual -gradually changing the axis of Saturn’s rotation. But the observed tilt of the planet is greater than one would expect. Why? Only a powerful event can interrupt this.
So, scientists have come up with a new hypothesis. The dislocation of a moon, which was previously in the Saturn system, would cause a further imbalance. It thus changed the planet’s inclination about 160 million years ago, precisely at the time of the formation of Saturn’s rings. The team performed a total of 390 simulations of this phenomenon.
A named month “Chrysalis”
In some scenarios, the lost moon collides with Titan or Iapetus, another natural satellite of the planet; in others, it is completely expelled from the Saturn system. But in 17 of the simulations, the moon passed Saturn, where it could have been cut by the forces of gravity, eventually forming the iconic rings.
The lost Moon was baptized Chrysalis, Chrysalide in French, by Jack Wisdom, comparing the emergence of Saturn rings to a butterfly emerging from a cocoon. Scientists believe that Chrysalis is smaller than our own Moon, and about the same size as another Saturn satellite, Iapetus. However, the latter is mostly composed of water ice.
“So it is plausible to hypothesize that the Chrysalis is also made of water ice, and that is what is needed to make the rings”, which is made up of 99% of it, said the professor. Does he feel that he has finally solved the mystery of Saturn’s rings? “We made a great contribution”he replied before adding: the Saturn system and its satellites are still in hiding many mysteries ».
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