Ganymede is the largest moon in the Solar System, bigger than the planet Mercury, and the only moon known to generate its own magnetic field.
At a glance
| radius | 2,630 km (0.413 × Earth) |
|---|---|
| distance from its planet | 1.07 million km |
| one orbit | 7.15 days |
| reflects | 43% of the sunlight it gets |
Read off the piece’s own catalogue, the same values it draws with.
About Ganymede
Ganymede is a world of rock and ice, larger than Mercury though less massive. Its surface mixes old, dark, heavily cratered regions with younger, brighter terrain crossed by grooves and ridges, where the icy crust was once pulled apart. Inside, it is layered, with an iron core whose churning produces a magnetic field strong enough to carve out a small magnetosphere within Jupiter’s.
That field gives away an ocean. Observations of Ganymede’s aurora with the Hubble Space Telescope showed that the way it rocks back and forth is damped, as it would be by a deep layer of salty water beneath the ice, matching hints from the Galileo spacecraft.
Ganymede is the main destination of the European Space Agency’s JUICE mission, which is planned to end its tour by going into orbit around it, the first spacecraft to orbit a moon other than our own.
What you see in the piece
Ganymede is lit only by the sunlight it reflects, and orbits between Europa and Callisto. Near Jupiter you can see it clearly; from another star, it cannot be seen at all.
Questions
What is the largest moon in the Solar System?
Ganymede, Jupiter’s moon, with a radius of 2,630 km, larger than the planet Mercury.
Does Ganymede have an ocean?
Very likely. The behaviour of its aurora, observed by Hubble, points to a salty liquid-water ocean deep beneath its icy crust.