Ganymede
5,268 kmacross
Ganymede is 5,268 km across and orbits Jupiter at 1,070,400 km, once every 7.2 days. The largest moon in the solar system — bigger than the planet Mercury — and the only moon with its own magnetic field.
▶ Visit Ganymede in 3D
Why this moon matters
Ganymede out-sizes the planet Mercury and is the only moon known to generate its own magnetic field, from a molten iron core. Like Europa it hides a saltwater ocean beneath its icy crust. ESA’s JUICE spacecraft is en route to orbit it in the 2030s — the first time any moon other than our own will have its own dedicated orbiter.
If it orbited the Sun instead of Jupiter, Ganymede would comfortably qualify as a planet.
Ganymede by the numbers
Diameter
5,268 km
Distance from Jupiter
1,070,400 km
Orbit period
7.2 days
Rotation
tidally locked
Surface gravity
1.43 m/s²
Temperature
−163 °C
Orbital speed
10.9 km/s
Sunlight travel time
43 minutes
In the interactive view you can fly to Ganymede directly and ride along as it circles Jupiter.
Keep going
✓ Facts verified July 2026
Every figure on this page is a real, rounded value checked against primary sources. Found something out of date? See how we keep it accurate.