Saturn's icy sponge
It's well-established by now that we're absolute suckers for weird and/or mysterious things floating around in space, and so far -- in terms of our little solar system, at least -- Saturn and its general neighborhood have been a gold mine for spacey weirdness. (Its moon Titan's seas of possibly life-containing opaque methane are a prime example.) The newest Saturnalian weirdo on the block, however, is another, much smaller moon: Hyperion. Just 300km across, it's one of the most irregular (read: funny-shaped) orbiting bodies in the solar system. Discovered in 1847 and photographed distantly by Voyager II in 1981 and again more closely by Cassini in 2005, new image processing of Cassini's hi-res holiday snaps has revealed much more than just a lumpy rock with a funky orbit. Turns out, as you can see from the resulting image, that it's incredibly porous, not unlike a giant floating loofah, and as a result about 40% of Hyperion is nothing but empty space. Hyperion's porousness allows its craters to stay remarkably well-preserved; the deepest is more than 1/3rd of the diameter of the entire moon and up to 10km deep. In any case, all we can say is: neeaaat.
For a higher-res version of this photo, check out NASA's website.