In December 1995, the probe that had been released by the Galileo spacecraft in July 1995 entered Jupiter’ atmosphere. Galileo had traveled 2.3 billion miles since its launch in October 1989. It spent the first 3 years in the inner solar system. During one flyby in Venus and two flybys of Earth, it gathered enough velocity from the gravity of the planets to reach Jupiter. Throughout its long journey, Galileo had been sending data about solar system back to Earth.
Galileo plunged into Jupiter’s crushing atmosphere on Sept. 21, 2003. The spacecraft was deliberately destroyed to protect one of its own discoveries – a possible ocean beneath the icy crust of the moon Europa.
Galileo changed the way we look at our solar system. The spacecraft was the first to fly past an asteroid and the first to discover a moon of an asteroid. It provided the only direct observations of a comet colliding with a planet.
Galileo was the first to measure Jupiter’s atmosphere.
You can find more info from http://solarsystem.nasa.gov/galileo/?CFID=29877228&CFTOKEN=25257562