Mimas and the F ring

This Cassini photo, released today, of the F ring crossing Mimas is from the "just plain cool" department. The F ring is a narrow, dim, dusty, braided thing that orbits Saturn just outside the main A and B rings; the main rings, and Saturn, would be off the screen to the left of this photo.

I checked the actual brightness of the pixels in Photoshop, to see if it was true that the core of the F ring has the same brightness all the way around, and I got a surprise. Where the F ring crosses space, the pixels have values of around 100 out of 255, which is fairly dark. But where the F ring crosses Mimas, it's actually brighter -- not darker, as my brain is trying to convince me -- with a value of about 120 out of 255; there must be some light from Mimas leaking through the dusty ring, or maybe the image compression bled some light from adjacent areas into the narrow stripe of the F ring. Shows you what my brain knows.