To visit Ganymede, we need to get up close to the king of planets, Jupiter. On our approach to the Jovian system, we encounter a bow-shock wave where the solar wind is deflected by the planet’s magnetosphere, the largest and most dominant in our Solar System after the Sun. Jupiter requires respect. We are also greeted by the Galilean moons. These objects hold together a list of superlatives in our Solar System: the biggest moon (Ganymede), the most geologically active moon (Io), the object with the smoothest surface (Europa), the most densely cratered moon (Callisto) and the only moon to have a magnetosphere (Ganymede).