jupiter's moon,biggest satellite in our solar system
Ganymede was discovered by Galileo Galilei on January 7th ,1610.It was discovered with the other Jovian moons,"Io,Europa,and Callisto"
40% of the terrain is dark and cratered,the other 60% is light and grooved(sulcus).The older layers are older and thought to be the original crust.Lighter areas are newer and smooth.The biggest area was named the "Galileo" region.
Ganymede's average distance from Jupiter is 665,115 miles(1,070,400 km).Each rotation takes about 7.16 days .Each orbit takes 7.16 days as well.
Ganymede is larger than Mercury,but only half its mass.If it orbited the Sun instead of Jupiter it would be easily classified as a planet.Only known moon to have a magnetosphere(a magnetic field surrounding the planet)