Osmium Remembers

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Science  19 Apr 2002:
Vol. 296, Issue 5567, pp. 475-477
DOI: 10.1126/science.1070515

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Natural radioactive substances with long half-lives can provide remarkable insights into the history of our planet. In his Perspective, Carlson highlights the insights into mantle convection that can be gained from studying osmium isotopes in rare osmium minerals. As Meibom and Frei show in their report, osmium isotope ratios carry a signature from the early core. The results suggest that at least some portions of the mantle circulate to the crust and the core several times over Earth history and that the solid inner core began to form within 250 million years of Earth's formation.