Pluto's moon Charon is the best sidekick a dwarf planet could hope for: Unwavering in its loyalty, content to be a minor character in somebody else's narrative. But two years after the New Horizons flyby, the largest of Pluto's five moons is finally getting some well-deserved time in the spotlight. New research suggests that Charon's storied history includes tectonic activity, cryovolcanism and, perhaps, a globe-spanning ocean.