Gerald Wasserburg
The Caltech geochemist whose super-clean laboratory dated Moon rocks and found the traces of aluminium-26 in the Allende meteorite.
Key facts
- Born
- 1927
- Died
- 2016
- Nationality
- American
- Field
- Geochemist
Gerald Joseph Wasserburg served in the US Army in the Second World War, then studied geology and became a professor at the California Institute of Technology. He was a master of measuring tiny amounts of isotopes with extreme precision.
His laboratory, nicknamed the Lunatic Asylum, built a new kind of mass spectrometer and worked under very clean conditions. When the Apollo missions brought back Moon rocks, his group dated them with great accuracy, helping to show when the great lunar basins formed and when the dark lava plains erupted.
In 1976, with Typhoon Lee and Dimitri Papanastassiou, Wasserburg found something remarkable in the white inclusions of the Allende meteorite. They contained extra magnesium-26, made by the decay of radioactive aluminium-26, which has a half-life of only about 700,000 years. That meant aluminium-26 had been alive in the young Solar System when these first solids formed, perhaps made in a nearby star shortly before.
Aluminium-26 is now thought to have been the main source of heat that melted the first asteroids. Its decay also serves as a fine clock for the first few million years of the Solar System. Wasserburg won many prizes, including the Crafoord Prize, and an asteroid is named after him.