Cassini 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 kilometers 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 Sept. 30, 2015.
The view was obtained at a distance of approximately 25,000 miles (41,000 kilometers) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 64 degrees. Image scale is 804 feet (245 meters) per pixel.
The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.
Credit: NASA/JPL-Caltech/Space Science Institute