Flying Over Plutos Moon Charon . ... Next, recent analysis of data taken by the robotic New Horizons spacecraft that shot past Charon -- the namesake that is the largest moon of Pluto -- in July now indicates that the cause of the huge chasm that runs across the 1200-km moon was that a huge internal sea froze. ... To better picture the crack, a fanciful journey over some of Charon's has been digitally created from collected images. ... New Mirror: Follow APOD in Portuguese on Facebook . ...