We all know Saturn as the big outer planet with the rings. Why does Saturn have such beautiful ring structure? Astronomers aren't entirely sure, but they must have formed back when Saturn was just an infant planet. Astronomers can, however, explain the existence of Saturn's outermost ring, the E ring. Where did this ring come from? The culprit is Saturn's Moon Enceladus!
Above is a recent image taken by the Cassini spacecraft which is currently orbiting Saturn and its moons. As you can see, there appears to be some material erupting from the surface of the moon, and indeed there is! Enceladus experiences what we call cryovolcanism, which means that it has volcanoes which spew water and ammonia when they erupt instead of hot rocky lava. These eruptions are so intense that the material actually leaves the planet and travels into outer space! Since Saturn's rings are so close to Enceladus, the water and other molecules get caught up in Saturn's gravitational field and form the outermost ring. This ring is technically unstable, which means the material will stay for a short time, but then be lost forever into space. That's no big deal though, because Enceladus is continually erupting and adding new material to the E ring.
Image credit: NASA/JPL-Caltech/Space Science Institute
