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The Moons and Rings of Jupiter

Jupiter Family Portrait A Miniature Solar System
The planet Jupiter's four largest moons are called the Galilean satellites, after Galileo Galilei who discovered them in 1610. These moons, named Io, Europa, Ganymede, and Callisto, are particularly intriguing since each has its own amazing distinction in our Solar System.

Galilean Moons: Io
Io is the most active volcanic body in the Solar System, and parts of its surface often change within weeks.
More on Io


Galilean Moons: Europa
Europa's cratered surface is mostly water ice, and there is strong evidence that it may be covering an ocean or water or slushy ice.
More on Europa


Galilean Moons: Ganymede
Ganymede is the largest moon in the Solar System (larger than even the planet Mercury), and is the first moon known to have its own magnetic field.
More on Ganymede


Galilean Moons: Callisto
Callisto is extremely heavily cratered, but has surprised scientists by yielding evidence support the existence of its own subsurface ocean, deep enough inside the moon that it does not affect the surface.
More on Callisto

Did you know?

Thirteen of Jupiter's 16 known moons were discovered from Earth.
The other three were first seen by Voyager.

The Surface of Io
Io's Volcanic Surface

Europa's Icy Surface
The icy plains of Europa

Bright Terrain on Ganymede
Ganymede's Terrain

Craters on Callisto
Craters on Callisto

The Four Galilean satellites, arranged by size.
Four Galilean satellites, arranged by size.
From left: Ganymede, Callisto, Io and Europa.

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Last updated 10/01/01.

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