Saturn’s Rings May Be Younger Than Thought—and Disappearing

Data from NASA’s Cassini mission points to the rings being no more than 400 million years old—quite young in the planet’s 4.5-billion-year history

One of Cassini's last looks at Saturn and its main rings from a distance, produced by combining images taken in October 2016. NASA / JPL-Caltech / Space Science Institute

Saturn’s famous rings may be a relatively new feature of the gaseous planet—and they might not be here to stay, a trio of recent studies suggests. The three papers, all published in mid-May, analyzed data from NASA’s Cassini spacecraft, which orbited Saturn from 2004 to 2017 and collected information on the planet’s moons, atmosphere and rings. 

Because Saturn’s rings are mostly made up of ice chunks—and a small percentage of tiny rock particles—they darken with time as cosmic dust accumulates on them. This can be useful for figuring out how old the ice chunks are. 

“Think about the rings like the carpet in your house,” Sascha Kempf, a physicist at the University of Colorado Boulder who led one of the studies, published in Science Advances, says in a statement. “If you have a clean carpet laid out, you just have to wait. Dust will settle on your carpet. The same is true for the rings.”

By analyzing 163 grains of dust from outside the Saturn system that Cassini gathered from its rings, scientists estimated the hoops are no more than 400 million years old—and they may still have been forming when dinosaurs roamed the Earth. Compared to Saturn’s 4.5-billion-year existence, that makes its rings relatively young.

Yet, one of the studies, published in Icarus, estimates that the rings may also be ephemeral—they might only last another 15 million to 400 million years. Meteoroids that bombard the hoops of ice cause some of their material to drift inward toward Saturn. Every second, the rings are losing several tons of mass, writes CNN’s Ashley Strickland. 

Given how, on a cosmic scale, the rings likely have not been—and won’t remain—around for very long, “we’re quite lucky to see a ring in the first place,” Kempf tells Science News’ Nikk Ogasa. 

Over time, Saturn’s rings may begin to look more like the darker, thinner ones surrounding Uranus and Neptune, which may once have been as large and brilliant as what we now see around Saturn, Paul Estrada, a research scientist at NASA’s Ames Research Center and a co-author of all three studies, explains in a statement

The age of Saturn’s iconic hoops has been a matter of debate among scientists for years. Even after these new studies, not all are convinced the rings are a recent addition. If, for example, a process not yet known to researchers is clearing dust from the rings, they could be much, much older than they appear, “possibly as old as Saturn” itself, Aurélien Crida, a planetary scientist at Côte d’Azur University in France who was not involved in any of the studies, tells Science News.

The new research may not entirely settle the debate, and it doesn’t solve the long-standing mystery of how Saturn’s rings formed in the first place. But it lays the foundation for future studies, which may provide more clues into the rings’ origin.

“In studying the universe, we often think about origins—origins of galaxies, stars and planets,” Indiana University astronomer Richard Durisen, a co-author on two of the papers, says in a statement. “But planets are incredibly active and diverse systems where new things happen all the time. If Saturn’s rings are not as old as the planet, that means something happened in order to form their incredible structure, and that is very exciting to study.”

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