This composite of the Galilean Satellites shows images of the moons taken by the Galileo spacecraft. Details of their surfaces are given in the lower two rows of the composite, including features produced through volcanism, ice, and cratering.
Click on image for full size
The Galilean satellites are the 4 major moons of Jupiter, Io
, and Callisto
. In this picture, Io, and Io’s surface, are shown on the left-most end, then Europa, and its surface, then Ganymede, then Callisto. Of Jupiter’s 60 moons, these four are the biggest.
These moons were discovered by Galileo Galilei in 1610. Their discovery by Galileo provided the key piece of evidence for Galileo's proof that the Earth was not the center of the Universe. Although Galileo initially thought they were stars, through continued observations over a couple of weeks, he realized that the objects he had observed remained in the vicinity of Jupiter. He was finally able to show that these objects were orbiting Jupiter, thus proving that not all objects in the heavens orbited the Earth.
Interestingly, Galileo named these natural satellites of Jupiter the "Medicean satellites" , after the famous Medici family of Renaissance Italy. The colorful names we now use for these satellites can be attributed to Simon Marius (who claimed to have observed the satellites before Galileo in 1609, but did not publish his findings). Marius attributed the suggestion of these names to a suggestion from Johannes Kepler in 1613.
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This drawing shows the positions of the four Galilean satellites relative to each other, and the path of the Galileo spacecraft on one of its flyby's past Jupiter. Of the four Galilean satellites, Io is...more
Jupiter has // Call the moon count function defined in the document head print_moon_count('jupiter'); moons and a ring system. The four Galilean satellites; Io, Europa, Ganymede, and Callisto, are among...more
Rhea was discovered by G. Cassini in 1672. Rhea is the 5th farthest moon from Saturn, with a standoff distance of 527,040 km. It is one of the icy moons, similar to the Galilean satellites. Rhea is about...more
Tethys was discovered by G. Cassini in 1684. Tethys is the 8th closest moon to Saturn, with a standoff distance of 294,660 km. It is one of the icy moons, similar to the Galilean satellites. Tethys is...more
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Several interesting phenomena are found at the poles of Jupiter, the largest planet in our Solar System. Three of Jupiter's four large "Galilean" moons are ice-covered and thus reminiscent of Earth's polar...more