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Wallner, A.*; Froehlich, M. B.*; Hotchkis, M. A. C.*; Kinoshita, N.*; Paul, M.*; Martschini, M.*; Pavetich, S.*; Tims, S. G.*; Kivel, N.*; Schumann, D.*; et al.
Science, 372(6543), p.742 - 745, 2021/05
Times Cited Count:41 Percentile:96.52(Multidisciplinary Sciences)Half of the chemical elements heavier than iron are produced by the rapid neutron capture process (r-process). The sites and yields of this process are disputed, with candidates including some types of supernovae (SNe) and mergers of neutron stars. We search for two isotopic signatures in a sample of Pacific Ocean crust-iron-60 (Fe) (half-life, 2.6 million years), which is predominantly produced in massive stars and ejected in supernova explosions, and Pu (half-life, 80.6 million years), which is produced solely in r-process events. We detect two distinct influxes of Fe to Earth in the last 10 million years and accompanying lower quantities of Pu. The Pu/Fe influx ratios are similar for both events. The Pu influx is lower than expected if SNe dominate r-process nucleosynthesis, which implies some contribution from other sources.