Deep inside some of NASA’s most venerable space probes lie plutonium-filled hearts beating to warm and power the robots, which include the twin Voyager spacecraft, Cassini before its daring plunge through Saturn’s rings and New Horizons trekking through the rubble of the Kuiper Belt.
But in the wake of the Cold War, the U.S. stopped producing its own plutonium. For a while, NASA could run its missions solely off existing or imported plutonium. But thanks to a change in the space agency’s partnership with the Department of Energy, last summer, fresh American plutonium once again left Earth inside NASA’s Mars-bound Perseverance rover — and more missions will do so in years to come. And for scientists who focus on the outer solar system, that’s vital.
