[ispom]

http://www.gemini.edu/index.php?option=content&task=view& id=244

deep inside Charon could water be liquid.
the rudimentary radioactivity deep in the interior making that the water stay liquid there.
but there is fresh ice on the surface, meaning that some liquid water must somehow reach the surface. The ammonia sitting on the surface provides the clue. It’s the ammonia that helps keep some material liquid

the probe "New Horizons", which will arrive at this system in 2015 can verify that Gemini results.