First spotted by the Voyager spacecraft thirty years ago, it wasn’t until Cassini that the linear features criscrossing Saturn’s moon Dione known as “wispy lines” were confirmed to be the icy faces of high cliff walls rising hundreds of feet from the moon’s frozen surface. Possibly caused by tectonic activity Dione’s cliff walls shine brightly in the sunlight, being made of reflective water ice and too steep for darker surface material to build up upon.
The image above was taken on December 20, 2010, by the Cassini spacecraft at a distance of about 67,000 miles (107,000 km). The view is of the trailing side of Dione, which, like many moons, always keeps one side facing toward its parent planet as it orbits.
Dione is 698 miles (1,123 km) wide. It is about as far away from Saturn as the Moon is from Earth.
See the full release and more images on the Cassini Imaging Lab site here.
Image: NASA / JPL / Space Science Institute
Here’s some awesome just-released raw images from Cassini’s flyby of Dione earlier this morning! The low angle of sunlight brings out the detail of the moon’s rugged terrain, peppered with ancient craters of all sizes and gouged by long scars of steep, icy cliffs.
Fantastic! Thanks to team leader Carolyn Porco for alerting us to these images today via email…and be sure to check out several more images on the Cassini imaging team site here.
Image credits: NASA/JPL/Space Science Institute
A closer look at the surface of Rhea, Saturn’s second-largest moon, reveals some of its signature “wispy lines”…the bright exposed faces of steep cliffs on the icy 950-mile-wide moon.
Taken by the Cassini spacecraft on June 3, 2010, the image above has been level-adjusted to bring out surface details. Being composed of 75% water ice, Rhea is highly reflective and the original raw image was a bit overexposed.
Image: NASA/JPL/Space Science Institute
The heavily creased and cratered face of 700-mile-wide Dione is partially lit by the Sun in this image from Cassini, taken on March 4. Some of the moon’s characteristic “wispy lines” can be seen along its sunlit limb…these are the bright, exposed walls of icy canyons caused by ancient tectonic activity. The darker surface material that covers the rest of the moon can’t stick to these sheer cliffs, some many hundreds of feet high, and as a result they remain highly reflective to sunlight.