Who would have thought that Pluto is a graffiti artist, spray-painting one of its moons, Charon, with a reddish stain that covers an area the size of New Mexico?
Charon’s polar coloring comes from Pluto itself – methane gas that escapes from Pluto’s atmosphere becomes “trapped” by the moon’s gravity and freezes to the cold, icy surface at the moon’s pole. This is followed by chemical processing by ultraviolet light from the sun that transforms the methane into reddish organic materials called tholins. Find out more: http://go.nasa.gov/2cK2LSR
