Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

1 Publication
Time-Resolved Two Million Year Old Supernova Activity Discovered in the Earth’s Microfossil Record
Ludwig, P.; Bishop, S.; Egli, R.; Chernenko, V.; Deneva, B.; Faestermann, T.; Famulok, N.; Fimiani, L.; Gómez-Guzmán, J.; Hain, K.; Korschinek, G.; Hanzlik, M.; Merchel, S.; Rugel, G.;
Massive (>10M_⊙) stars, which terminate their evolution as core collapse supernovae (CCSN), are theoretically predicted 1 to eject >10-5M_⊙ of the radioactive isotope 60Fe (half-life t1/2=(2.61±0.04) Ma; weighted average of Ref. 2 and 3). If such an event occurs sufficiently close to our solar system, one expects that traces of the supernova (SN) debris could be deposited on Earth. Since 60Fe has no or little expected anthropogenic or cosmogenic production mechanisms, its detection in terrestrial reservoirs would be an immediate proxy for a past Earth-SN interaction within the past few million years. Herein, we report for the first time a time-resolved 60Fe signal residing, at least partially, in a biogenic reservoir. Using the experimental technique of accelerator mass spectrometry (AMS), this signal was found through the direct detection of live 60Fe atoms contained within secondary Fe-oxides, among which are magnetofossils 4; the fossilized chains of magnetite crystals produced by magnetotactic bacteria 5, 6. Magnetofossil preservation precludes post-depositional Fe mobilization events, ensuring that the 60Fe record is correctly preserved. The magnetofossils were chemically extracted from two Pacific Ocean sediment drill cores. Our results show that the 60Fe signal onset occurs around 2.7 Ma, near the lower Pleistocene boundary, terminates between 1.4 Ma and 1.8 Ma, and peaks at about 2.2 Ma.
Keywords: accelerator mass spectrometry, AMS, supernova, cosmogenic nuclide
  • Open Access LogoProceedings of the National Academy of Sciences of the United States of America 113(2016)33, 9232-9237
    DOI: 10.1073/pnas.1601040113

Publ.-Id: 22837 - Permalink