科学60秒:土星环——卫星的残迹
Today, Saturn's only massive moon is Titan. But Saturn’s fellow gas giant planet Jupiter has four big moons. So Saturn might once have had more—one of which could have had a rocky core surrounded by a shell of water ice. That moon would have interacted with a disk of gas surrounding Saturn at the time, dragging its orbit closer and closer.
As the moon ______3_____, tidal forces would have flexed its icy shell, stripping off chunks to build rings a thousand times more massive than Saturn has today. Eventually, ice boulders in the rings would have ______4____ each other, spreading out the rings, and causing the outer edge to spawn icy moons—the small ones we find orbiting Saturn today.
As for that ancient moon’s rocky core? Saturn probably _____5_____. Leaving Titan unique. And leaving scientists with a puzzle they finally may have solved.
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