Deep-Sea Astronomy with Accelerator Mass Spectrometry

Accelerator Mass Spectrometry (AMS) is a highly sensitive method to measure extremely low isotopic ratios of long-lived radionuclides relative to its stable isotope. Inspired by findings of an excess of ⁶⁰Fe in a ferromanganese crust approximately 2 Myr ago, which was interpreted to be of supernova-origin, we use this method to determine concentrations of a variety of radionuclides in deep-sea sediment samples covering a time range from 1.7 to 3.2 Myr.
An international collaboration of different AMS facilities is utilized to search for signatures of ²⁶Al, ⁵³Mn, and ⁶⁰Fe above terrestrial background production and extraterrestrial influx. In addition, the cosmogenic radionuclide ¹⁰Be is measured to confirm existing magnetostratigraphic dating of the samples and for comparison with atmospheric production ratios of ²⁶Al/¹⁰Be. All ¹⁰Be and ²⁶Al measurements arefinished, ⁵³Mn and ⁶⁰Fe is in progress. Measurement results and the influence of different background sources on a potential supernova signature will be presented and discussed.