Plutonium is a radioactive actinide metal that tarnishes when exposed to air and forms a dull coating when oxidized.
Core Principles & Analysis
Glenn Seaborg's team first produced plutonium in early 1941 by deuteron bombardment of uranium at Berkeley's 60-inch cyclotron, and the discovery was kept secret until after World War II.
Fissile plutonium-239, with a 24,110-year half-life, fueled the 'Fat Man' bomb dropped on Nagasaki in 1945 and remains a core material of nuclear arsenals and mixed-oxide reactor fuel.
Heat from decaying plutonium-238 (half-life 87.7 years) powers radioisotope generators aboard the Voyager probes, New Horizons, and the Curiosity and Perseverance Mars rovers.