In a paper published this month, DTM cosmochemists report the discovery in a meteorite of dust grains with extremely high contents of the rare isotope chromium-54. These tiny (100 nanometer, or less than 0.1% the width of a human hair) grains were found in a sample of the highly primitive meteorite Orgueil from which most of the minerals had been dissolved in acids, leaving acid-resistant Cr-rich oxide grains. Isotopic imaging with DTM’s NanoSIMS ion microprobe revealed that some of the grains have ratios of ⁵⁴Cr to the more abundant isotope ⁵²Cr more than ten times higher than any other materials found in the Solar System. These unusual compositions point to an origin in the cooling ejecta of a supernova explosion before the formation of the Sun. These grains may be responsible for long-observed small variations in the Cr isotopic composition of bulk meteorites and planets. If so, the authors argue that their heterogeneous distribution lends support to a hypothesis that a supernova explosion seeded the forming Solar System with dust grains and radioactive elements.

The work is led by former Carnegie Fellow Liping Qin and is co-authored by DTM’s Larry Nittler, Conel Alexander, Richard Carlson and Jianhua Wang, and Washington University’s Frank Stadermann. The paper was published in the January 15 issue of Geochimica et  Cosmochimica Acta.

To read paper in full, click here.