Arriving at Europa, the sixth biggest moon in our Solar System, we immediately get a sense for why, within the space of a few decades, this moon became as alluring to astrobiologists as the planet Mars. From orbit, Europa is a perfect white sphere. In fact, it is one of the smoothest surfaces of any known solid object in the Solar System. We are far from the heavily cratered surface of Callisto, or the rugged terrains of Ganymede, as the tallest features on Europa are jagged ‘blades’ of ice that measure in the tens of meters, not hundreds. Standing on its surface, space travelers would observe a uniformly flat horizon everywhere they looked, like being on a giant snooker ball.