Ganymede is the biggest moon in the solar system. It's wider than the planet Mercury.
It's the only moon with its own magnetic field, which makes glowing auroras over its poles.
By watching those auroras rock back and forth, scientists worked out that a salty ocean lies deep under the ice. It may hold more water than all of Earth's.
Europe's JUICE spacecraft is on its way. In 2034 it will become the first spacecraft ever to orbit a moon other than our own.
- Width
- 5,268 km
- Goes round Jupiter
- every 7.2 days
- One day
- The same: it always shows Jupiter one face
- Temperature
- about −160 °C
- 70 kg on Earth weighs
- 10 kg here
