If you were to fly over Enceladus' southernmost regions, you'd witness a remarkable sight. With surprising frequency, this ice-covered moon spurts a plume of water into space - a telltale sign that a global ocean lies underneath. Scientists have struggled to explain how such a tiny moon could sustain enough energy to maintain a liquid ocean, but new research shows that a porous core could do the trick, and that Enceladus has been wet for billions of years - a potential sign of habitability.