Key facts
- Scale fact
- 5,260 kmdiameter
- Estimated age
- ~4.5 billion years
- Composition
- Water ice, silicate rock, metallic iron core and probable saltwater ocean
- Temperature
- ~90-160 K surface
Ganymede
5,260 kmdiameter
Visual creditJuno 2021 / NASA / JPL-Caltech / SwRI / MSSS / Kevin M. Gill / CC BY 2.0Source: Wikimedia Commons
Details
Ganymede is Jupiter's largest moon and the largest moon in the Solar System, bigger than Mercury. It is also the only known moon with its own magnetic field, and evidence points to a buried saltwater ocean beneath its icy shell.
Galileo detected Ganymede’s intrinsic magnetic field, the only one known around a moon, consistent with a convecting metallic core. Hubble measurements of how its auroral belts shift in Jupiter’s magnetic environment strengthened the case for a buried saltwater ocean.
The surface preserves both dark, old cratered terrain and brighter grooved regions fractured by tectonic stress. Together with gravity and magnetic data, those terrains support a differentiated interior of metal, rock, water and multiple ice layers rather than a uniform frozen body.
Links
- Universe journey
- Asteroid belt & Jupiter
- Wikipedia
- Ganymede on Wikipedia
Size neighbors
Objects near Ganymede on the scale
Sources
References for Ganymede
Measurements and descriptive context are compiled by the Scale of Space team from the references below. If you find an error, please let us know.
- Ganymede — Wikipedia
- Visual reference: Wikimedia Commons (Juno 2021 / NASA / JPL-Caltech / SwRI / MSSS / Kevin M. Gill, CC BY 2.0)
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About
Scale of Space is a scroll-based journey through the universe, placing objects on a single logarithmic scale so you can compare size across an unbroken range.
Guides explain selected parts of that range, while focused views filter the objects by subject.