Pluto’s four smallest moons might have formed after its biggest moon, Charon , suffered an impact, rather than being a chip off the dwarf planet.

The Pluto system is an oddity in the solar system. The largest of its five moons, Charon, is 1200 kilometres across, almost half the size of the dwarf planet. By comparison, Pluto’s four smaller moons – Styx, Nix, Kerberos, and Hydra – are tiny, measuring no more than 50 kilometres across. They also orbit very close to both Pluto and Charon, just tens of thousands of kilometres away. …