Dione (false-color image) 2005. Fourth-largest moon of Saturn, orbiting at about the same distance as our Moon orbits Earth. It has a varied terrain, is probably made mostly of water ice with a rocky core, and has a tenuous atmosphere. (Image: NASA/JPL/SSI) ©Mona Evans, &quot;10 Amazing Facts about Saturn&#x27;s Moons&quot; http://www.bellaonline.com/articles/art28136.asp