Crescent Moons...

Caption NASA originale:"Rhea and Enceladus shared the sky just before the smaller moon passed behind its larger, cratered sibling.

This image is part of a "mutual event" series in which one moon passes close to or in front of another. These sequences help scientists refine the orbits of Saturn's moons.

Cratered Rhea is 1.528 Km (about 949 miles) across and presumed to be geologically dead. While much smaller, Enceladus (505 Km, or about 314 miles across) is geologically active today.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 4, 2006 at a distance of approx. 1,4 MKM (such as about 800.000 miles) from Rhea and 1,9 MKM (such as about 1,2 MMs) from Enceladus. The view was obtained at a Sun-moon-spacecraft, or phase, angle of about 142°, relative to both moons.
Image scale is 8 roughly Km (about 5 miles) per pixel on Rhea and roughly 11 Km (about 7 miles) on Enceladus".