Sure. Europa has a liquid ocean of water under its ice. But Europa is small and should be frozen solid. So you need a source of energy to melt that water ice. It turns out that the tug of gravity from Jupiter, Io and Ganymede create tides in Europa that pull and tug on it; this generates energy as the internals flex and rub up against itself. In the earth, the moon, creates tides that we see at the ocean, but it also creates tides in the earth itself, some 2-3 feet at the equator. Enceladus has a pool of liquid that is heated from the push and pull of the gravitational tug of war between Saturn and Titan.

Pluto, however, has no source of tidal energy input. Pluto and Charon are in a gravitational equilibrium; there is no tug of gravity inputting energy into either body, or at least there does not appear to be. Because Pluto and Charon are tidally locked to each other both in revolution and rotation, there is no push-pull like in the other small bodies listed above.

So, why is there so much gas above the surface of Pluto? Where did it come from? Why is the surface of Pluto so young and crater free?

And yea, this excites me. I've seen Pluto with my own eyes through a 25" telescope as nothing more than a very faint dot that barely moved over two nights. Now, that dot is a whole world with strange geology. I'm going to do an outreach event tonight showing 200-300 people Saturn, and I expect a lot of Pluto questions as well.