The Galileo spacecraft arrived at Jupiter in 1995. It consisted of a probe to descend into the Jovian atmosphere and an orbiter to transmit pictures and other data from 11 scientific instruments. En route to the gas giant, it provided close-up images of two asteroids, Gaspra and Ida.
In December of 1995, the probe descended at 160 kilometers/hr. (100 miles/hr.) into Jupiter's clouds. For five hours before entry, the probe sent back information on lightning, radio emissions, and the magnetic field. The Galileo orbiter has investigated the atmosphere of Jupiter and the surface composition of its satellites. After each orbit of Jupiter, the spacecraft's trajectory was gravity-assisted by encounters with one of Jupiter's moons. In this manner, there were numerous encounters with the moons of Jupiter, some within 500 kilometers (310 miles) of the surface.
Galileo imagery has revealed surface features on Europa (one of Jupiter's large icy moons) that suggested the presence of subsurface water. In September 2003, the mission ended as the orbiter plunged into Jupiter's atmosphere in order to avoid a future collision with Europa that could impact future studies of that moon and its subsurface ocean.
Jupiter And Its Four Largest Moons
This composite of imagery from Galileo shows Jupiter's Great Red Spot and, from top to bottom, Io, Europa, Ganymede, and Callisto. The Great Red Spot is a storm that is more than 300 years old.
Europa's Icy Terrain
Ridges and bands of ices with different compositions crisscross this area of Europa that is about 100 miles (160 km) wide.
On its way to Jupiter, Galileo captured this view of Gaspra, an asteroid that is about 12 miles (19 km) long.