DTM staff member Richard Carlson and Carnegie fellow Maud Boyet are featured for their insightful work into Earth’s early history in the September 2005 issue of Physics Today. The article, “Radioisotopic Tracers Reveal Extensive Melting in Earth’s Distant Past,” describes the pair’s new and more precise measurements of the neodymium isotope ratio (¹⁴²Nd/¹⁴⁴Nd) in chondritic material—a ratio that can vary with the decay of the now-extinct radioactive isotope ¹⁴⁶Sm. This research demonstrates that ¹⁴²Nd/¹⁴⁴Nd is measurably higher in terrestrial rocks than it is in the chondritic material from which the Earth is thought to have formed. Boyet and Carlson conclude that within the first 30 million years of the solar system’s formation, the chemical composition of the Earth’s mantle underwent significant change.

The article’s author concludes, “Either Earth was formed from stuff fundamentally different from chondritic meteorites, the building blocks of planets—unlikely, considering the hot, well-mixed conditions in the early solar system—or the part of Earth that geochemists have access to is not representative of Earth as a whole.” Stan Hart of the Woods Hole Oceanographic Institution predicts “wall-to-wall neodymium-142 work” to emerge in the next couple of years. Hart added, “When I read their paper, my head just went nuts.”

The full article can be found in the September 2005 issue of Physics Today or can be accessed by subscribers on the Physics Today website.