![Introducton](https://webarchive.library.unt.edu/eot2008/20080921230827im_/http://www2.jpl.nasa.gov/galileo/graphics/jupintrotitle.gif)
![](https://webarchive.library.unt.edu/eot2008/20080921230827im_/http://www2.jpl.nasa.gov/galileo/graphics/1tp.gif)
The Moons and Rings of Jupiter
![](https://webarchive.library.unt.edu/eot2008/20080921230827im_/http://www2.jpl.nasa.gov/galileo/graphics/1tp.gif)
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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.
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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
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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
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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
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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
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![Did you know?](https://webarchive.library.unt.edu/eot2008/20080921230827im_/http://www2.jpl.nasa.gov/galileo/graphics/didyousmll.gif)
Thirteen of Jupiter's 16 known moons were discovered from Earth.
The other three were first seen by Voyager.
![](https://webarchive.library.unt.edu/eot2008/20080921230827im_/http://www2.jpl.nasa.gov/galileo/graphics/1tp.gif)
![The Surface of Io](https://webarchive.library.unt.edu/eot2008/20080921230827im_/http://www2.jpl.nasa.gov/galileo/graphics/iosurfacef.jpg)
Io's Volcanic Surface
![](https://webarchive.library.unt.edu/eot2008/20080921230827im_/http://www2.jpl.nasa.gov/galileo/graphics/1tp.gif)
![Europa's Icy Surface](https://webarchive.library.unt.edu/eot2008/20080921230827im_/http://www2.jpl.nasa.gov/galileo/graphics/eursurf.jpg)
The icy plains of Europa
![](https://webarchive.library.unt.edu/eot2008/20080921230827im_/http://www2.jpl.nasa.gov/galileo/graphics/1tp.gif)
![Bright Terrain on Ganymede](https://webarchive.library.unt.edu/eot2008/20080921230827im_/http://www2.jpl.nasa.gov/galileo/graphics/ganyterrain.jpg)
Ganymede's Terrain
![](https://webarchive.library.unt.edu/eot2008/20080921230827im_/http://www2.jpl.nasa.gov/galileo/graphics/1tp.gif)
![Craters on Callisto](https://webarchive.library.unt.edu/eot2008/20080921230827im_/http://www2.jpl.nasa.gov/galileo/graphics/callicraters.jpg)
Craters on Callisto
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