Saturn's rings are one of the most recognized features of the solar system, but scientists don't know how they got there. New data suggest they're older than some theories suggested.
Space Science Institute/JPL-Caltech/NASA/Reuters
New evidence from the US-European Cassini mission to Saturn suggests a very early birth for ices in Saturn’s spectacular system of rings and moonlets, dating back to shortly after the planet itself formed.
The results deepen a mystery that has bedeviled Saturn watchers since Galileo first spotted what later would be interpreted as rings in 1610: How did the rings form? And, more recently, what sustains the ring system?
“No one actually knows why the rings can survive for 4.5 billion years,” says Scott Kenyon, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. “At the moment, we don’t have a good model” that explains this longevity.
The apparently implausible life span of the ring system has led some researchers to propose that the system didn’t form shortly after the planet did.
Instead, it might have formed perhaps 100 million years ago. The raw material for the rings and moonlets could have come from the debris spawned by a collision between close-in moons, or between a close-in moon and a comet.
But the recent-ring scenario has had a troubled existence.