Pluto and its largest moon, Charon, are shown to scale in these images from New Horizons, which flew past Pluto in 2015. Charon probably formed when the young Pluto was smashed by another large body, blasting debris into space. The debris formed a ring around Pluto, and much of it then coalesced to form Charon, which is much darker and more battered than Pluto. [NASA/JHUAPL/SwRI]