Dione and Enceladus

Dione_EnceladusAlthough Saturn’s moons Dione (in the foreground) and Enceladus are made of more or less the same stuff, Enceladus has a considerably higher reflectivity than Dione. Therefore, it appears brighter against the blackness of space.

Enceladus has a constant rain of ice grains from its south polar jets which cover its surface with a bright snow. Dione’s older, weathered surface has slowly gathered dust and radiation damage, darkening through a process known as “space weathering.”

Image Credit: NASA

Enceladus Close Up

Enceladus close upDuring its close flyby last Wednesday of the active south polar region of Saturn’s moon Enceladus, the Cassini spacecraft grabbed this view of the terrain below. It’s centered on terrain at 57° S latitude by 324° W longitude. The spacecraft was about 124 km from Enceladus. The image resolution is 15 m per pixel.

Image Credit: NASA

Dione Close Up

Dione chasmsSome parts of the surface of Saturn’s moon Dione are covered by linear features, called chasmata, in dramatic contrast to the round impact craters that cover most moons. The bright network of fractures on Dione was seen in poor resolution Voyager images and was called “wispy terrain.” The actual nature of this terrain was unclear until Cassini photos showed we weren’t seeing something like surface deposits of frost but a pattern of bright icy cliffs among myriad fractures. This stress pattern may be related to Dione’s orbital evolution and the effect of tidal stresses over time.

Image Credit: NASA