- is the largest moon of Jupiter 
- a large, icy, outer moon that has marks on it from impact craters and various parallel faults 
- 3,400 miles/5,268 kilometers in diameterIt   
- orbits Jupiter at a mean distance of 664,000 miles/1,070,000 kilometers 
- has a magnetic field and i said to have probably have a molten iron core 
- takes 171.75 hours/7.15 Earth days to orbit Jupiter
- has a mass of 1.48 * 1023 kg 
- independently discovered by Galileo and S. Marius in 1610 
- largest moon in the solar system (larger than the planet Mercury), If not bound to Jupiter, it would be considered a planet in its own right
- Geologists think that it used to have plates, like the Earth, but they froze together soon after Ganymede's birth