Formation of Pluto’s moons. 1: a Kuiper belt object approaches Pluto; 2: it impacts Pluto; 3: a dust ring forms around Pluto; 4: the debris aggregates to form Charon; 5: Pluto and Charon relax into spherical bodies. Smaller pieces became the irregularly-shaped moons Nix, Hydra, Kerberos and Styx. Credit: Wikipedia