Jets of icy particles burst from Enceladus, one of Saturn's moons, on Nov. 27, 2005. This striking image is one of a number shown off by researchers at a Dec. 5, 2005, meeting in San Francisco of the American Geophysical Union.
This montage shows four major icy moons that the orbiter Cassini visited while surveying the Saturnian system during 2005. A large number of craters on Rhea and Iapetus suggests that those moons have been most exposed to meteors. Dione appears to have smoother regions, with the lower number of craters suggesting a slightly younger surface; a large system of fractures indicates tectonic activity. A region near the south pole of Enceladus is strangely devoid of impact sites; scientists suspect it was geologically active in the recent past.
The variations in these false-color views relate to geologic features. The origin of the shading isn't clear, but may be caused by subtle differences in the surface composition or the sizes of grains making up the icy soil.
This close-up of Rhea's surface shows craters within craters. Time takes a toll: Scientists say the icy surface material probably has been pummeled into a fine powder.
Besides being hit by celestial objects, Hyperion suffers from erosion. At 174 miles in diameter, it is the largest known irregularly shaped moon in the solar system.