Discovered by Galileo Galilei in 1610 with three other Jupiter moons, Europa, Io, and Callisto, Ganymede is the 7th moon Jupiter’s 67 moons.
|Discovered By:||Galileo Galilei January 7, 1610|
|Mass:||1.48 x 10^23 kg (2.0 Moons)|
|Orbit Distance:||1,070,400 km|
|Orbit Period:||7.16 days|
|Surface Temperature:||-163 °C|
These four moons are called Galilean moons and Ganymede is so larger that if it was orbiting a Sun instead of Jupiter, it would be considered a planet.
Just a bit smaller than Mars, Galileo originally called Ganymede Jupiter III, but later renamed by German astronomer Johannes Kepler after a mythological Greek Trojan prince who was a cupbearer for the gods.
With twice the mass of our Earth, Ganymede is the largest moon in our Solar System.
Scientists have long thought that if Jupiter had a larger mass it would be a gas giant that experienced nuclear fusion, turning it into a sun.
It has many moons in its orbit that could have been planets. Ganymede is the only moon within our solar system that has its own magnetic field.
Although very light, it’s believed that the field was created due to the liquid iron core at Ganymede’s center. But the magnetic field isn’t the only thing that makes Ganymede notable.
It is made up of layers of water ice and silicate rock in almost equal amounts, and scientists believe that there just might be liquid saltwater under its thick crust of ice.
Researchers think that this water may be as close to the surface as 124 miles and that it is next to the moon’s rocky mantle.
This theory would make Ganymede an excellent candidate for finding potential life. There is a thin atmosphere of oxygen on Ganymede but it isn’t great enough to be life supporting.
Another interesting thing about Ganymede is that it is thought to have tectonic activity that builds up heat and friction, causing the surface to have activity that covers the impacts from comets and asteroids.
Dark areas cover 40% of the surface and may be impacts from around 4 billion years ago.
There are lighter areas that are not that old, with grooves that scientists believe are due to the tectonic activity.
Ganymede is tidally-locked to Jupiter. This means that it has one side that faces the planet and one side that faces away from the planet.
The moon is orbiting Jupiter at 24,321 mph/39,165 kmh, and it takes Ganymede 7.16 Earth days to complete one Jupiter orbit.
Surface temperatures on Ganymede average -171 F to -207 F during daytime areas and at night it can reach -193 C.
Scientists are very interested in Ganymede and there have been quite a few spacecraft flybys that have gathered data on this moon.
The early missions in the 1970’s offered only blurred images, however, the later 2007 New Horizon mission sent back incredible detail on the topography and make up of Ganymede.
So far, there have been six space missions that have flown by Ganymede.