One of the 8 planets revolving around the sun is Jupiter. It is the largest planet in the solar system and was discovered by Galileo Galilei in the year 1610. Approximately 60 moons have been discovered orbiting Jupiter and Ganymede is its largest moon.

Here are some lesser known facts about Jupiter’s moons:

Jupiter and its satellites have been named after Greek gods and goddesses.

Since 1973, 4 spacecrafts have been sent in close proximity to Jupiter for images and astronomical observations. The names of the spaceships were Pioneer 10 and 11 and Voyager I and II.

Ganymede’s orbital period is 7.15 days and since its orbital period is the same as the time taken for revolution on its own axis, only one side of Ganymede is visible to Jupiter just as in the case of Moon and Earth.

Jupiter’s largest satellites were discovered by Galileo and are therefore referred to as the Galilean moons.

Ganymede is larger in size than Mercury. The other three major satellites, Io, Europa and Callisto are larger than Pluto.

Almost 300 years after Io’s discovery, several close-up images of the moon were taken by the Voyager spacecraft. Due to the continuous volcanic eruptions that take place on Io’s surface, filling the craters with lava, the surface of Io is relatively smooth making it one of the youngest looking celestial body surfaces in the solar system.

Hot volcanic eruptions emit poisonous gases and the atmosphere of Io primarily comprises of sulphur dioxide. Its surface appears reddish orange in colour. Io is the innermost in the orbit of Jupiter amongst the Galilean moons.

Jupiter’s 4 major satellites, all exist in orbital resistance with Jupiter.

Europa’s surface comprises mostly of water and ice. Due to the presence of tidal heating, cracks and fissures can be found on the surface. Europa is mostly devoid of craters which make scientists conclude that Europa might only be a few million years old.

Ganymede has a lot in common with Europa in terms of surface appearance. Ganymede’s surface is also made of water and ice. Celestial photos reveal dark and light spots on its surface. The lighter regions are believed to be comparatively younger than the dark regions.

Callisto can be defined as a typical outer solar system satellite. It has a number of craters and an icy surface. Scientists have discovered that Callisto might have a salty ocean and rocky interiors underneath the icy surface. Callisto’s age is estimated to be 4 billion years.

Lack of mountains on the surface of Callisto proves that it may not have any tectonic activity on its surface. Callisto also has a strong magnetic field.

Callisto with a diameter of 4806 km is the third largest moon in the entire solar system.

The interiors of Ganymede, Europa and Io are believed to be somewhat similar to that of Earth comprising of a core and a mantle containing partial solid rock and a coating of sulphurous compounds.

Some of the other moons of Jupiter that have been discovered include Leda, Thebe, Megaclyte, Autonoe, Hermeppe, Arche, Herse, Kore, Sinope, Elara, Locaste, Euporie, Himalia, Amalthia and more.