A beautiful look at the Saturn moon Dione and a great look at a rayed crater. Easy to see why the rays are so bright being made of what we would think of as “super hard water ice”.
I believe this crater is Creusa. The rays are as you would expect material ejected out after an impact, in this case water ice (we think). These rayed craters on Dione may be less than about 50 M/yr’s -old (1). Yes, sounds like a long time but really not so much when you think about things on a solar system-evolutionary time scale. Cassini has shown us that at least parts of the Saturn system are quite active more so than many people first belived.
NASA – Cassini captured this striking view of Saturn’s moon Dione on July 23, 2012. Dione is about 698 miles (1,123 kilometers) across. Its density suggests that about a third of the moon is made up of a dense core (probably silicate rock) with the remainder of its material being water ice. At Dione’s average temperature of -304 degrees Fahrenheit (-186 degrees Celsius), ice is so hard it behaves like rock.
The image was taken with Cassini’s narrow-angle camera at a distance of approximately 260,000 miles (418,000 kilometers) from Dione, through a polarized filter and a spectral filter sensitive to green light.
The Cassini spacecraft ended its mission on Sept. 15, 2017.