How Saturn Got Its Rings
A sophisticated computer model demonstrates how tidal forces on Saturn could have peeled away the icy outer layers of a large moon that occupied an unfortunate piece of real estate. After pulling off the ices, the gravity of Saturn would have doomed the moon's silicate core, tugging it closer and closer until it smashed into the planet, the simulation shows. The theory neatly accounts for why Saturn's rings are nearly pure ice, while most objects in that part of the solar system are more an ice-rock blend. Planetary scientist Aurélien Crida, with the Université de Nice Sophia-Antipolis, France, notes that the stripped-off ice would have swirled in rings about 1,000 times more massive than what exist today.