Two Moons That Pass in the Night

This image shows the rare sight of Saturn's moons Mimas and Pandora aligning in the night sky—and they couldn't look more different.

Seeing them both together makes you realise just how varied moons can be. Pandora, the smaller of the two—just 50 miles across—lacks the mass, and hence sufficient gravity, to pull itself into the neat, spherical shape of its sibling Mimas. Meanwhile Mimas looks rather like the Death Star.

This images was acquired with Cassini's narrow-angle camera, and each pixel represents 4 miles. The satellite was 690,000 miles from Mimas and 731,000 from Pandora at the time, and as you can probably guess, the lines across the image are Saturn's rings. [NASA]