Cassini views Helorus in half-light

NASA's Jet Propulsion Laboratory Press Release

Image credit: NASA.
Image credit: NASA.

NASA’s Cassini spacecraft captures a crater duo on Saturn’s moon Dione that is superimposed on older, linear features. The upper of the pair, named Italus, is overprinted on a grouping of ancient troughs called Petelia Fossae. The lower crater, Caieta, sits atop a feature named Helorus Fossa.

Scientists are confident that Helorus and features like it are very old, both because there are many old craters on top of it and because of the way that material has apparently filled in the shallow valley, giving its edges a softer appearance. Fossae on Dione (698 miles or 1,123 kilometres across) like Helorus are believed to be tectonic features, formed when the area between tectonic faults drops down into trough-like structures.

This view is centered on terrain at 22 degrees south latitude, 73 degrees west longitude. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on 30 September 2015.

The view was obtained at a distance of approximately 25,000 miles (41,000 kilometres) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 64 degrees. Image scale is 804 feet (245 metres) per pixel.

Saturn: Exploring the Ringed Planet

Find out more about Saturn and its moons in this 196-page special edition from Astronomy Now. Order from our online store.