Triton is the largest of blue Neptune’s moons, and the only round one.This moon is high on the list of researchers’ places to send a spacecraft, because it sports so many strange qualities. Triton is on a “retrograde” orbit, revolving in the opposite direction of the planet and other moons, suggesting it could have been a captured, Pluto-like body. From its surface rise bizarre ice volcanoes, making it one of the farthest bodies in the solar system known to have active geophysics. Triton’s sibling, Neptune’s second largest moon, Proteus, is also pretty unusual. Rather than being round, this moon is shaped like what mathematicians call an irregular “polyhedron” (a solid object with many plane faces), and what “Dungeons and Dragons” nerds know as a 20-sided dice. Proteus’ surface is pinkish-red, perhaps the result of complex organic compounds like hydrocarbons.