In this week's issue of Science, Rick Carlson, geochemist Mary Horan, and former postdoctoral fellow Maud Boyet, now at the Université Jean Monnet, St. Etienne, France, argue that isotopic variability of barium, neodymium, and samarium measured in carbonaceous chondrites reflect distinct stellar nucleosynthetic contributions to the early solar system. The paper is entitled “Chondrite Barium, Neodymium, and Samarium Isotopic Heterogeneity and Early Earth Differentiation.”

By using ¹⁴⁸Nd/¹⁴⁴Nd to correct for the observed s-process deficiency, the group produced a chondrite ¹⁴⁶Sm-¹⁴²Nd isochron consistent with previous estimates of the initial solar system abundance of ¹⁴⁶Sm and a ¹⁴²Nd/¹⁴⁴Nd at average chondrite Sm/Nd ratio lower (by 21 ± 3 parts per million) than that measured in terrestrial rocks. Their finding strengthens the conclusion that the ¹⁴²Nd deficiency in chondrites, relative to terrestrial rocks, reflects ¹⁴⁶Sm decay and early planetary differentiation processes.