Dione and Rhea are moons of Saturn, and this Cassini spacecraft shot of them makes it look like they're some sort of giant microorganism (macroorganism? Cosmoorganism?) undergoing mitosis.
In reality, Dione (top) is passing in front of Rhea (bottom) from Cassini's viewpoint. There are three coincidences making the pair look like one giant peanut-shaped object: 1) Dione is slightly smaller than Rhea, but closer, so they appear to be the same size in the picture; 2) they have about the same albedo (reflectivity) so shades of the moons match, blending them together better; and 3) there is a giant crater on the south end of Dione that lines up with the point where they overlap, tricking your brain into seeing the junction point as the waist of a peanut.
As much as I love this picture, the one of Rhea on top of Titan was cooler, so that one made it into the Top 14 instead of this.Get the hi-res version here.Image credit: NASA/JPL/Space Science Institute