Ganymede Facts

Galileo Galilei discovered Ganymede in 1610. It is Jupiter’s largest moon and is also the biggest natural satellite in the Solar System. Ganymede is named after a Trojan prince was carried off to Olympus in the shape of an eagle to become the Greek god’s cupbearer.

How was Ganymede discovered?

Galileo Galilei discovered Ganymede on January 7th, 1610. The discovery was made with three other moons, Io, Europa and Callisto. These four moons are known as the Galilean Moons.

It was this discovery by Galileo that led to our understanding that planets revolve around the Sun.

How did Ganymede get its name?

Galileo first named the moon Jupiter III. However, the numerical system of the naming of planets and satellites was abandoned in the mid-1800s in favour of ancient gods. The moon was named after a Trojan prince in Greek mythology called Ganymede, who was turned into an eagle by Zeus and made the official cupbearer of the Greek Gods.

Ganymede is the only Galilean moon named after a male character.

Geological Facts

  • Ganymede is 4.5 billion years old.
  • Ganymede is the largest natural satilitte in our Solar System, bigger than the planet Mercury.
  • Although it is bigger than Mercury, it is less dense, with a mean radius of 1,635 miles (2,631.2 km).
  • Ganymede is the only natural satilitte in the Solar System to have a magnetosphere, which is typically found in planets.
  • The natural satellite has a liquid core of iron.
  • It has an internal ocean which could hold more water than all of planet Earths oceans combined.
  • The surface of Ganymede is covered in two types of terrain: dark regions and lighter regions.
  • The darker region covers 40% of the surface and has numerous craters.
  • The lighter region makes up 60% of the surface and has grooves that form elaborate patterns and give the moon its characteristic look.
  • Ganymede’s grooves can be as high as 2,000 ft and stretch for thousands of miles. They were formed by tectonic activity and water being released from below the surface.

Orbital Facts

  • Ganymede orbits Jupiter.
  • Ganymede is estimated to be 665,000 miles (1.070 million kilometres) from Jupiter.
  • It takes seven Earth-days to orbit Jupiter.
  • The average speed of Ganymede as it orbits Jupiter is 10.880 km/s.

Related:Which planet has the most moons?

Origin Facts

  • Ganymede was formed by an accretion of dust and gas from Jupiter when it was formed.
  • It took 10,000 years for Ganymede to form from, where Callisto, another Jupiter moon, took 100,000 years.
  • The moon was formed closer to Jupiter where the dust and gas were denser which is why the moon took a shorter time to form.

Expeditions to Ganymede

  • Both Pioneer 10 in 1973, and the Pioneer 11 mission in 1974, passed by the moon and gathered information about Ganymede.
  • Voyager 1 and 2 both passed by Ganymede in 1979, and data collected from this mission found that the moon was bigger than Saturn’s
  • moon Titan.
  • A spacecraft in 1995 called Galileo orbited around Jupiter and between 1996 and 2000 made six flybys of Ganymede.
  • It was during the Galileo space mission in 1996 that scientists discovered the magnetosphere.
  • The last space mission to recorded data of Ganymede was New Horizons which was making its way to Pluto.
  • The European Space Agency has a mission planned called Jupiter Icy Moon Explorer (JUICE), which will explore the Jovian moons in 2022. This mission will pay particular attention to Ganymede and will remain in orbit around Jupiter’s largest satellite.
  • The Russian Space Research Institute is assessing a Ganymede Lander (GL) mission, which will focus on studying the astrobiology of the moon.

Related Questions


Picture of Ganymede

Image of Ganymeda (moon)

Ganymede Quick Facts

Mass:148,185,846,875,052 billion kg (0.025 x Earth)
Diameter:5,262.4 km
Equatorial Circumference:16,532.3 km
Orbit Distance from Jupiter:1,070,400 km
Orbit Period:7.15455296 Earth days
Mean Surface Temperature:-163.15°C
First Record:January 7, 1610
Recorded By:Galileo