The surface appears to be extremely young. There are no craters on these mountains. They're apparently made of ice and are relatively tall. http://www.nytimes.

The surface appears to be extremely young. There are no craters on these mountains. They're apparently made of ice and are relatively tall. http://www.nytimes.com/2015/07/16/science/pluto-flyby-photos-reveal-mountains.html http://www.nytimes.com/2015/07/16/science/pluto-flyby-photos... "But these mountains are almost certainly made of frozen water instead of rock."