Galileo was NASA’s first spacecraft to orbit Jupiter.
Launched on October 18, 1989, Galileo reached Jupiter on December 7, 1995, after using gravity assists at Venus and Earth. It released an atmospheric probe before entering orbit around Jupiter. The probe descended into the planet’s atmosphere and transmitted measurements of temperature, pressure, wind, and chemical composition before the environment ended its operation.
From orbit, Galileo studied Jupiter’s clouds, magnetic field, radiation belts, rings, and major moons. It found strong evidence that Europa has a salty ocean beneath its icy surface and observed volcanic activity on Io. The mission also examined Ganymede and Callisto, revealing complex geological histories.
Pioneer 10 and Pioneer 11 flew past Jupiter earlier, but neither entered orbit. Voyager 1 and Voyager 2 also performed flybys. NASA ended Galileo’s mission in 2003 by directing it into Jupiter’s atmosphere, preventing an accidental impact on Europa.