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Data from Cassini’s last ring-diving orbits has now strengthened the hypothesis that Saturn’s rings formed very recently, just a few hundred million years ago.
Saturn acquired its jewels relatively late in life. If any astronomers had gazed at the sky in the time of the dinosaurs, they might have seen a bare and boring Saturn.
It was then that some sort of catastrophe struck the gas giant. Perhaps a stray comet or asteroid struck an icy moon, tossing its remnants into orbit. Or maybe the orbits of Saturn’s moons somehow shifted, and the resulting gravitational tug-of-war pulled a moon apart. However it happened, two new lines of evidence from Cassini make it clear that the rings were not around in the early days of the solar system 4.5 billion years ago, as scientists had long believed, says Jeff Cuzzi, a ring specialist at NASA’s Ames Research Center in Mountain View, California. “It rules out the primordial ring story,” Cuzzi says. “That’s what it looks like to me.”
At the moment there is no consensus on what might have caused the rings formation so recently.