Just outside the orbit of Mimas lies the moon Enceladus. Though the two moons are similar in size, mass and compostition, they are very different worlds indeed. The diameter of Enceladus is 500 km, and it lies 238 x 103 km from Saturn. Enceladus takes only 1.3 days to orbit Saturn.

     Enceladus is so bright and shiny that it reflects nearly 100 percent of the light that shines upon it. The surface of this moon is apparently covered with icy crystals which do all this reflecting. These crystals may be icy ash from active volcanos on Enceladus.

     There is also a strong possibility that Enceladus and Saturn's E ring have a connection. The particles that make up the E ring are bright and reflective like those on Enceladus. Either particles from the ring are falling down onto Enceladus, or Enceladus is supplying the ring with particles.

      Though a definite answer is not known, evidence point to Enceladus as the source for the ring particles. The E ring is being disrupted by the solar wind and is losing particles. It must therefore, be getting replenished from somewhere. Secondly, there are not many craters on the surface of Enceladus, and that suggests that something covers the craters up soon after impact. Volcanoes are the most likely culprit.

     Voyager spacecraft images of Enceladus show what look like lava flows, except that in this moon's case, it would be icy water flows. No geysers or active volcanos have been found, but they are probably the only answer that makes sense to the question of Enceladus' surface and the E ring particles.

     Just why Enceladus would be geologically active is another mystery. Jupiter causes such activity on its moons, but Saturn exerts only one forth the tidal stress on its moons. Enceladus is not big enough to have internal heat or pressures create volcanos, and the moons around it should not have any gravitational effect either. Such answers may have to wait until the Cassini spacecraft reaches Saturn.