1. Discovered in 1610 by Galilei Galileo who called them the Medicean Stars
2. The names given to the four moons of Jupiter come from Greek mythology but were not used until the 20th century. Ganymede is the name of the son of King Tros.
3. Largest moon in the solar system, larger than Mercury but with about half the mass because it is made up primarily of icy water and silicate rock.
4. Ganymede doesn’t rotate as it orbits; the same side of Ganymede always faces Jupiter.
5. It takes 7 days and 3 hours to complete a single orbit around Jupiter
6. Diameter: 5262 km or 3,269 miles; Distance from Jupiter: 1,070,000 km or 664,000 miles; Orbital period: 7.2 days
7. 3 way orbital resonance with Io and Europa called the Laplace Resonance. Io orbits