Spheres...

Original caption:"Saturn's sibling moons, Rhea and Dione, pose for the Cassini spacecraft in this view.
Even at this distance, it is easy to see that Dione (below) appears to have been geologically active in the more recent past, compared to Rhea.
Dione's smoother surface and linear depressions mark a contrast with Rhea's cratered terrain.
Sunlit terrain seen on Rhea (1.528 Km, or 949 miles across) is on the moon's Saturn-Facing Hemisphere. Lit terrain on Dione (1.126 Km, or 700 miles across) is on that moon's Leading Hemisphere. North is up.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Nov. 1, 2005, at a distance of approx. 1,8 MKM (about 1,1 MMs) from Rhea and 1,2 MKM (approx. 800.000 miles) from Dione. The image scale is 11 Km (about 7 miles) per pixel on Rhea and 7 Km (about 4 miles) per pixel on Dione".