Now that Cassini has returned to Saturn's equatorial plane, it has lots of opportunities to observe Saturn's moons. For about a week, Cassini has been taking regular sets of images of Iapetus, which I've assembled into an animation.
I've been resisting all urges to speculate on what kinds of geological features are present on Ceres, until now. Finally, Dawn has gotten close enough that the pictures it has returned show geology: bright spots, flat-floored craters, and enigmatic grooves.
I've been out of town for a couple of days and am overwhelmed with work and an overflowing email box. So what do I do about that? I ignore what I'm supposed to be doing and play with Cassini raw image data, of course. Here is a "mutual event" of Mimas (the bigger moon) and Pandora (the outer shepherd of the F ring).
Clearly, this is Saturn, and its rings, and if you look closer you can see a tiny circle, on top of the rings, which is Mimas, and two stars in the background. It should look weird to you that while the rings are bright, Mimas is a black dot. What is happening here? Nearly everything in this picture is lit by light that has not arrived directly from the Sun.
About four years ago I wrote a blog entry about an ESA press release about paper published in Nature that suggested that Saturn's moons Tethys and Dione might have volcanic activity, like Enceladus. A new paper published in Icarus casts doubt on that conclusion.