Abundance of live 244Pu in deep-sea reservoirs on Earth points to rarity of actinide nucleosynthesis

• Published in: Nature communications 2015-01, Vol.6 (1), p.5956-5956, Article 5956
• Main Authors: Wallner, A., Faestermann, T., Feige, J., Feldstein, C., Knie, K., Korschinek, G., Kutschera, W., Ofan, A., Paul, M., Quinto, F., Rugel, G., Steier, P.
• Format: Article
• Language: English
• Subjects: 639/33/34; 704/158/47; Explosions; Humanities and Social Sciences; multidisciplinary; Physics; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms6956

Half of the heavy elements including all actinides are produced in r -process nucleosynthesis, whose sites and history remain a mystery. If continuously produced, the Interstellar Medium is expected to build-up a quasi-steady state of abundances of short-lived nuclides (with half-lives ≤100 My), including actinides produced in r -process nucleosynthesis. Their existence in today’s interstellar medium would serve as a radioactive clock and would establish that their production was recent. In particular 244 Pu, a radioactive actinide nuclide (half-life=81 My), can place strong constraints on recent r -process frequency and production yield. Here we report the detection of live interstellar 244 Pu, archived in Earth’s deep-sea floor during the last 25 My, at abundances lower than expected from continuous production in the Galaxy by about 2 orders of magnitude. This large discrepancy may signal a rarity of actinide r -process nucleosynthesis sites, compatible with neutron-star mergers or with a small subset of actinide-producing supernovae. The build-up of short-lived nuclides in the interstellar medium tells us about production frequency and yield of heavy elements by nucleosynthesis. Wallner et al . find a low abundance of live interstellar 244Pu detected from the deep-sea floor, suggesting a rarity for r-process nucleosynthesis sites.