NASA’s trusty Juno orbiter has been hanging around Jupiter for many years now. Its observations have taught us a lot about the gas giant and its intense storms. It revealed that the storms stretch farther into the planet than previously thought, and Juno is our primary eye in the sky when it comes to observing the swirling vortices that make Jupiter so iconic. But Jupiter isn’t Juno’s only target, and the spacecraft has also spent a great deal of time studying several of Jupiter’s moons, including Io and Europa.

Now, for the first time since the year 2000, Juno is going to make a close flyby of Ganymede, the largest moon of Jupiter and also the largest moon in the entire solar system. It’s even larger than Mercury by volume, but less than half as massive. What makes Ganymede so special isn’t just its size, but also the fact that it has its own magnetic field. As the only moon in our solar system with a magnetic field, it may be better protected against certain threats from space, though without a significant atmosphere it’s unclear whether life could exist there.