1991    The American Galileo spacecraft makes its closest approach to 951 Gaspra, becoming the first probe to visit an asteroid.

1995    The Galileo spacecraft arrives at Jupiter, a little more than six years after it was launched by Space Shuttle Atlantis during Mission STS-34.

1998    Data sent from the Galileo spacecraft indicates that Jupiter's moon Europa has a liquid ocean under a thick crust of ice.

2001    NASA's Galileo spacecraft passes within 112 miles of Jupiter's moon Io.