Claude Allègre is a geochemist whose innovative radioactive dating techniques have given us a better understanding of the Earth’s rocky outer layers — its mantle and crust. He pioneered the use of the decay of rhenium-187 to osmium, now widely used to date the mantle underneath continents. By using his techniques to analyse meteorites, Claude has also provided important insights into the make-up of the early Solar System.
Radioactive dating compares the relative concentrations in rocks of radioactive elements and the ones into which they decay. Many of these elements — such as argon and xenon — are very rare. Claude developed instruments that set new standards of sensitivity and precision.