Ganymede

Moon· orbits Jupiter

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, evidence of a subsurface ocean.

Open in 3D viewSee Ganymede in the live, interactive 3D map

Key facts

Mass

1.48 × 10²³ kg

0.0248 M⊕

Radius

2,631 km

1.51× wider than our Moon

Surface gravity

1.43 m/s²

15% of Earth's

Day length

7.2 days

Orbit around Jupiter

7.16 Earth days

Science

Physical

Mass: 1.48 × 10²³ kg · 0.0248 M⊕
Radius: 2,631 km · 1.51× wider than our Moon
Density: 1,942 kg/m³ · 1.9× water
Surface gravity: 1.43 m/s² · 15% of Earth's
Escape velocity: 2.74 km/s · 25% of Earth's

Orbit around Jupiter

Distance from Jupiter: 2,373,889 km
Orbital period: 7.2 days
Eccentricity: 0.001
Inclination: 0.20 °

Rotation

Rotation period: 7.2 days
Tidal locking: Tidally locked to its parent

Temperature

Minimum: 70 K (-203 °C)
Mean: 110 K (-163 °C)
Maximum: 152 K (-121 °C)

Composition

Bulk composition: Roughly equal parts rock and water ice, differentiated into an iron core, a rock mantle and a thick ice shell over a probable salty ocean.

Radiation & temperature

Insolation: 0.0357 S⊕ · 4% of the sunlight Earth receives
Bond albedo: 0.35 · reflects 35% of incoming sunlight
Equilibrium temperature: 109 K (-165 °C)
Measured mean temperature: 110 K (-163 °C)
Surface magnetic field: 719 nT · 1% of Earth's

Discovery & history

Discovered: January 7, 1610
By: Galileo Galilei
Method: Visual discovery (telescopic)
Name: Ganymede, a Trojan youth carried to Olympus by Zeus to be cupbearer to the gods. The name — like those of the other Galilean moons — was proposed by Simon Marius in 1614 at Johannes Kepler's suggestion; Galileo, who discovered them in 1610, called them the Medicean Stars and referred to them by number.

A Galilean moon found in 1610 and the largest moon in the Solar System — bigger than the planet Mercury, and the only moon with its own magnetic field.

Images

Ganymede in true colour, imaged by Galileo — NASA / JPL (public domain) · Wikimedia Commons

Juno Zooms in on Jupiter's Moon Ganymede — NASA/JPL-Caltech/SwRI/MSSS · NASA Image Library

Close-up of Dark Side of Jupiter Moon Ganymede — NASA/JPL-Caltech/SwRI · NASA Image Library

NASA's Juno Mission Explores the Magnetic Connection Between Jupiter and Ganymede — NASA/JPL-Caltech/SwRI/Duling · NASA Image Library

Hubble Catches Jupiter's Largest Moon Going to the 'Dark Side' — NASA/GSFC · NASA Image Library

Possible Moonwich of Ice and Oceans on Ganymede Artist Concept — NASA/JPL-Caltech · NASA Image Library

Eyeing Ganymede — NASA/JPL/University of Arizona · NASA Image Library

The Galilean Satellites — NASA/JPL/DLR · NASA Image Library

Images from open archives · credit shown per image