Saturn's rings are more massive and far older than previously thought, astronomers say.
The estimate is made by a University of Colorado team, harnessing a powerful computer model and using data from the US spaceprobe Cassini in orbit around the ringed giant.
The team computed gravitational forces and collisions in a sample of more than 100,000 icy particles in one of Saturn's rings.
Rather than orbiting smoothly around the planet, as had been the previous assumption, the particles tend to aggregate in denser clumps, they said.
As a result, the mass of material in the rings could be three times greater than thought.
The fragments also give an indicator of the rings' age, because they are reduced by repeated orbital collision over time, and by impact from meteorites, which also produce dust.
Saturn's rings could be “billions of years old,” compared with a previous estimate of around 100 million years, said lead researcher Larry Esposito in a press release.
He added it was unlikely that Saturn would be the lone planet in our galaxy to have huge rings.
“We humans are not just lucky to see rings around Saturn. This would lead us to expect massive rings also to surround giant planets circling other stars,” he said.
The findings were to be presented on Tuesday at the European Planetary Science Congress in Muenster, Germany.
Two hypotheses prevail as to how Saturn acquired its seven rings.
One is that the rings were born at the same time as the planet itself — they were left-over debris that became enslaved to the gas giant, doomed to orbit it for eternity.
The other theory, which has gained strength in light of other data sent back by Cassini, is that the rings were the remains of large icy moons that broke into smaller pieces over time.