Mean diameter: approximately 5,262 km · Orbits Jupiter.
Jupiter’s Ganymede takes first place, just ahead of Titan. It is wider than Mercury and is the only moon known to generate its own magnetic field.
Bright and dark terrains record different surface histories. This preliminary Juno image shows it through the camera’s green filter, not in natural color. Ganymede makes a fitting finale: a moon can be a complex world, not merely a small companion.
Sources: NASA moon guide · JPL size data.
Image source: NASA/JPL-Caltech/SwRI/MSSS; reuse terms. Resized and JPEG-compressed.