Moon Shadow Cap

Image source with more information
Credit: NASA/JPL/Space Science Institute

The first thing I thought on seeing this Cassini image was, "Wow!"

The next thing I thought was, "Wait... what am I looking at?"

You've probably noticed from other Cassini images that Saturn's rings, like any object with a suitable source of light, cast their own shadows. Gargantuan shadows, capable of swallowing up whole worlds if they're cast at the right angle. In this image we're looking down on the northern reaches of Mimas, which are cut across by the shadow of the rings bending around the moon's curved surface.

If you were standing on Mimas in one of the dark grey/very dark grey, but not quite pitch black areas to the left of this view, you'd see the sun shining through Saturn's rings. For us, however, the result is merely this eye-catching inverted-comma of a moon phase.