The discovery that some of the moons of the larger planets in our solar system have liquid water under the surface, and hence the potential to support life, came as a big surpise to scientists, as these moons were far outside the so-called “habitable zone” – the region nearer the sun containing Earth and Mars, and previously believed to be the only region capable of supporting life. The question then was, where did these moons get their warmth? Jonathan speaks with astrobiologist Tomas Paulech about just this question.