Cassini's Grand Finale: A Deliberate Farewell to Protect Enceladus and Unveil Saturn's Secrets

After 20 years in orbit, Cassini ended in 2017 with a controlled plunge into Saturn to prevent a fuel-depleted craft from contaminating Enceladus; its Grand Finale sent the orbiter on 22 dives through a 1,500-mile gap between Saturn's cloud tops and the inner edge of its rings, yielding landmark data on Saturn’s gravity, magnetic field, rings, and upper atmosphere, while Enceladus’s plumes revealed a subsurface ocean and organic chemistry. To avoid any contamination, Cassini carried plutonium-powered generators that would disperse if the craft burned up, ending the mission but leaving a vast scientific data legacy.