Charon: Icy Volcano World?

Explanation: An artist's conception of Charon (with Pluto in the background) against the backdrop of the Milky Way. The plumes and brighter spots depicted at left on Charon are thought to be created as water (with some ammonia hydrate mixed in) 'erupts' from deep beneath the surface. The material sprays out through cracks in the icy crust, immediately freezes and snows crystalline ice down onto the surface, creating a water-ammonia hydrate ice field.

Pluto

Image credit: Pluto and Charon models (enhanced), courtesy of Software Bisque. www.seeker3d.com, with plumes and ice fields added by Mark C. Petersen, Loch Ness Productions. Star field from DigitalSky 2, courtesy Sky-Skan, Inc.