Some 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
The Cassini spacecraft snapped this picture of the moon Dione orbiting Saturn. At 1122 km in diameter, Dione is the 15th largest moon in the Solar System. Its interior is probably a combination of equal masses of silicate rock and water ice.
This image of Saturn’s moon Dione shows a mixture of features: bright, linear features showing evidence of tectonic movant and impact craters. The tectonic features reveal that Dione has been heated and cooled since its formation, and scientists use those as clues to piece together the moon’s past. The impact craters are evidence of external debris striking the surface and tell about the environment in which the moon has existed over its history.
Cassini images of Saturn are generally oriented so that Saturn appears north up, but the spacecraft views the planet from all sorts of angles. Here, Saturn seems to sit askew as the tiny moon Dione looks on from lower left. The terminator, which separates night from day, is also tilted because the planet is nearing its northern summer solstice. As a result, the planet’s northern pole is in sunlight all throughout Saturn’s day.
