Mars is the place that most of our spacecraft, landers and rovers are studying, searching for any evidence that life ever existed somewhere else in the Solar System. The perfect environment for life to thrive. We’ve only had tantalizing hints that these oceans are there, but NASA is building a spacecraft that will study one of these worlds in detail: the Europa Clipper. And they’re not the only ones. The European Space Agency is building their own mission, the Jupiter Icy Moons Explorer.