Galileo was intentionally sent into Jupiter’s atmosphere in 2003.
After more than seven years studying Jupiter and its moons from orbit, NASA deliberately guided the Galileo spacecraft into Jupiter on September 21, 2003. The controlled impact ended the mission and prevented the spacecraft from accidentally colliding with Europa or another moon.
Planetary-protection concerns drove the decision. Galileo had not been sterilized to the stringent standards required for a possible life-detection mission, and scientists considered Europa a particularly important target because evidence suggested it could possess a subsurface ocean. Destroying Galileo in Jupiter’s atmosphere removed the risk of forward contamination.
Galileo had already made major discoveries, including evidence supporting an ocean beneath Europa’s ice, a magnetic field around Ganymede, and extensive volcanic activity on Io. Its separate atmospheric probe entered Jupiter in 1995, so the 2003 event refers to the orbiter’s final controlled plunge, not the probe’s earlier descent.