Kenneth Change, “Pluto’s Portrait From New Horizons: Ice Mountains and No Craters,” New York Times (July 16, 2015), http://www.nytimes.com/2015/07/16/science/pluto-flyby-photos-reveal-mountains.html?emc=edit_th_20150716&nl=todaysheadlines&nlid=32962000
[excerpted] The first surprise was the rugged topography — mountains up to 11,000 feet high. But these mountains are almost certainly made of frozen water instead of rock….Majia here: a mystery on the edge of the solar system. What caused the topography on Pluto and Charon?
A second surprise was that the dwarf planet’s surface was unmarred by craters.
“We have not yet found a single impact crater in this image,” Dr. Spencer said…
Weather and tectonics can erase craters, but both require heat to stir things up. And Pluto, small and far away, possesses no obvious sources of heat.
For moons of giant planets, the heat can come from tidal forces squeezing the moon, but the tidal forces between Pluto and Charon are small.
“We have to get a little more clever,” Dr. Spencer said…
… Beyond Pluto, New Horizons is now speeding into the Kuiper belt, which extends a couple of billion miles beyond Pluto and likely contains billions of icy worlds, including one, Eris, that is slightly smaller than Pluto yet more massive.
Craters on Charon are also few.