Astromat

Here, we report the mass-independent Nd isotope composition of the Bennu aggregate sample OREX-800117-110. We also present data for the terrestrial standard UB-N and the CM2 chondrites Murray and Murchison, which were used to monitor data quality. Mass-independent Nd isotope analyses were carried out at ETH Zurich (Switzerland) using a Triton TIMS. The composition of Bennu is -25.4 ± 2.3 (±2SE; n=1), 1023.3 ± 2.0, 1.8 ± 1.9, 1.3 ± 4.0 and 9.5 ± 9.9 for µ142Nd/144Nd, µ143Nd/144Nd, µ145Nd/144Nd, µ148Nd/144Nd and µ150Nd/144Nd, respectively, relative to the JNdi-1 synthetic standard. The Nd isotope data of Bennu overlaps with that of CI chondrites and Ryugu. Therefore, the composition of Bennu closely resembles our best estimate of the initial composition of the solar system. This confirms the mission hypothesis that Bennu formed in the carbonaceous reservoir, which consists of material that originated beyond the snowline.