Pluto is still active four and a half billion years into its history. It was expected that small planets like Pluto would cool off long ago and not still be showing geological activity. Pluto is, in fact, showing numerous examples of geological activity on a massive scale across the planet.

One of the implications of the discovery of the Kuiper Belt and its many small planets is that many scientists now think of the solar system as having not two but three zones.

Most of the oceans in the Solar System are deep beneath ice shelves.

Alan Stern Quotes