In Greek mythology, Dione was the daughter of Tethys, so we should perhaps not be surprised to see the two eponymous moons of Saturn together in this image from the Cassini mission.
In reality, the moons Tethys (1062 kilometres or 660 miles across) and Dione (1123 kilometres or 698 miles across) are not mother and daughter in any sense. They are perhaps more like sisters since scientists believe that they formed out of the same disc around an early Saturn.
Dione in this image is the upper moon, while Tethys is the lower.
This view looks toward the anti-Saturn side of Dione. North on Dione is to the right. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on 4 April 4 2015.
The view was obtained at a distance of approximately 2.4 million kilometres (1.5 million miles) from Dione. Image scale is 14 kilometres (9 miles) per pixel.
