A planet can turn into a star. Mercury has ice. On Venus, it rains metal. Earth isn't round. Mars is the only planet that is solely populated by robots. The volcanoes on Jupiter's moon, Io, erupt its lava into space. Saturn has a hurricane in the shape of a hexagon. Uranus' moons are named after Shakespeare characters. Neptune has a ring like Saturn that we can't see in photographs. The Moon's real name is Luna. The oldest planet, Methuselah, is 12.7...