jibberjabber1 writes with news of a study published in Nature (abstract) that suggests Saturn's rings were created after a Titan-sized moon fell into the planet's atmosphere while the solar system was still young. "One of the leading theories has been that either some of Saturn's many moons crashed into each other, or that an asteroid crashed into one of them — leaving debris that formed the rings. The trouble has been that Saturn's moons are half ice and half rock and the planet's seven rings are now as much as 95 per cent ice, Robin says. If the rings were formed by a moon-on-moon crash or an asteroid-on-moon crash, there would be more rock in the rings. Something had to have stripped away the outer ice of a moon, she says. Her theory starts billions of years ago when the planet's moons were forming. A large disk of hydrogen gas circled Saturn and that helped both create and destroy moons. Large inner moons probably made regular plunges into the planet, jostled by the disk of gas. These death spirals each took about 10,000 years and the key to understanding the rings' origins is what happened to them during that time. According to Robin's computer model, Saturn stripped the ice away from a huge moon while it was far enough from the planet that the ice would be trapped in a ring. The original rings were 10 to 100 times larger than they are now, but over time the ice in the outer rings has coalesced into some of Saturn's tiny inner moons, Robin says." In other astronomy news, the Geminid meteor shower is due to reach its peak tonight.
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