Jupiter's Moon, Ganymede: Facts & Diameter

Instructor: John Williams
Ganymede is the largest moon in our solar system, and the largest moon orbiting the planet Jupiter. It has many characteristics that are of interest to astronomers and scientists. In this lesson, we'll discuss Ganymede, its characteristics, and the facts that make it an interesting structure to study.


In 1610, Galileo Galilei, an Italian astronomer, identified four moons orbiting the planet Jupiter. These moons are collectively known as Galilean Moons, and are some of the largest bodies in our solar system outside of the planets. Since then, 67 moons have been identified orbiting Jupiter, each with unique physical properties and composition. The largest of these moons is Ganymede which is currently the largest identified moon in our solar system. Let's discuss some key facts about this moon.

Ganymede - largest moon of Jupiter

Ganymede's Characteristics

A moon is an object that orbits a planet or other large bodies in space. Ganymede, as mentioned in the introduction, orbits Jupiter, which is the largest planet in the solar system. It takes Ganymede approximate seven 'Earth days' to orbit Jupiter. Ganymede's diameter is approximately 3,273 miles, which makes it also wider than Mercury, the closest planet to the sun. In terms of mass, this moon is also the largest, although it has less mass than most of the other planets in the solar system. Interestingly enough, it is large enough to see with the naked eye.

Ganymede has an atmosphere (layer or layers of gases) that contains oxygen, ozone, and hydrogen. It also has a magnetosphere, which is an atmosphere that contains charged molecules controlled by a magnetic field. It is the only moon in the solar system to contain this arrangement.

Ganymede contains a core that is composed of iron, and this core is surrounded by a layer of ice and rock. The surface contains many craters, or deep depressions, and also has many intricate grooves that may have formed from shifting in the crust, or upper layer. Scientists also believe that Ganymede may contain saltwater ocean-like bodies beneath the surface above the core.

Core and layers of Ganymede
Layers of Ganymede

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