| Term: | Ganymede |
| Definition: |
The seventh and largest of Jupiter's known satellites. This Galilean satellite has a diameter of 5270 km, slightly larger than Mercury, a mass about 1.48 × 10^23 kg (about 2 Earth Moons); an orbital period of 7.155 days, and an eccentricity of e = 0.0015. It was discovered by Galileo and Marius in 1610. The mean surface temperature of Ganymede is -160 °C. It is the only moon known to have a magnetosphere. |