The great debate on Saturn’s rings is far from resolved , according to a new study published in the journal Nature Astronomy ,
For years, scientists have argued about the age of Saturn’s famous rings: are they ancient and date from the birth of the planet? Or did they form more recently, in the last 100 million years?
The latter hypothesis has gained traction in recent years , with multiple papers reporting that the rings could be even younger than the dinosaurs.
Observations of Saturn from the Voyager 1 and 2 spacecraft in 1980 and 1981 suggested that the rings could be younger than the planet, much younger. And in recent years, data from the Cassini spacecraft (2004-2017) seemed to realize the idea that Saturn’s rings are between 10 and 100 million years old. It seems Cassini didn’t have the last word either.
A team of researchers has reignited the debate over the age of Saturn’s rings with a study dating the origin of the ring system in the early solar system, long before the appearance of the dinosaurs.
The authors suggest that processes that preferentially eject dusty, organic material from Saturn’s rings, a “ring rain” that falls in part on Saturn’s clouds, could make the rings appear younger than they actually are. Cassini, in fact, encountered this rain of rings when it dove between Saturn’s rings and its upper atmosphere during its Grand Final in 2017.
The authors of the new study commented:
“Cassini’s dive through the rings during the mission’s Grand Finale in 2017 provided data that was interpreted as evidence that Saturn’s rings formed only a few tens of millions of years ago, when dinosaurs walked the Earth. . Gravity measurements taken during the dive gave a more accurate estimate of the mass of the rings, which are made up of more than 95% water ice and less than 5% rocks, organic materials and metals. The mass calculation was used to determine how long the pristine ice in the rings would need to be exposed to dust and micrometeorites to reach the level of other ‘pollutants’ that we see today ”. F or many, this solved the mystery of the age of the rings.
But not all scientists were convinced.
In an article on Saturn’s rings published in Scientific American in August, ring expert Luke Dones of the Southwest Research Institute explained the following:
“I have no objection to young rings. I just think that no one has come up with a more plausible way to do them. It requires an unlikely event. In other words, in the early solar system, when there was a lot of flying debris, it is easy to imagine the dynamic processes capable of creating the rings: the capture of debris by Saturn’s gravity or the rupture of comets, asteroids, or even small moons. Once the rings began to form, it is also easy to imagine that the separate ring particles collide with each other and break even smaller, spreading around Saturn to form its rings . “
Aurélien Crida, from the Observatory of the Côte d’Azur and lead author of the new study clarifies why he thinks the debate is not yet resolved:
“ We cannot directly measure the age of Saturn’s rings like the rings on a tree stump , so we must deduce their age from other properties such as mass and chemical composition. Recent studies have assumed that the dust flow is constant, the mass of the rings is constant, and that the rings retain all the contaminating material they receive. However, there is still a lot of uncertainty about all of these points and, when taken with other results from the Cassini mission, we think there is a strong case that the rings are much, much older. “
Crida and his colleagues argue in their research that the mass measured during the end of the Cassini mission is in “extraordinary agreement” with models of the dynamic evolution of massive rings dating back to the primordial solar system.
Researchers will continue to study Cassini’s grand finale data and the many other measurements the spacecraft made during its more than 13 years on Saturn for years to come. So the debate over the age of Saturn’s rings will likely continue.
Referencia: Aurélien Crida, Sébastien Charnoz, Hsiang-Wen Hsu, Luke Dones. Are Saturn’s rings actually young?Nature Astronomy, 2019; DOI: 10.1038/s41550-019-0876-y
