A radioactive iron isotope, Fe-60, was found in fossilized remains of bacteria. This isotope is formed almost only in supernovae. It was expected to be found in certain magnetotactic bacteria that live in the ocean. Those bacteria make tiny iron crystals within their cells. They get the iron from atmospheric dust that gets in the ocean. A nuclear astrophysicist, Shawn Bishop, thought that if they observed remains of the bacteria from certain sediments of the ocean (ranging from about 1.7-3.3 million years ago), they could remove any Fe-60 present in the sample. The researchers did this by chemically treating the samples to dissolve any unnecessary parts of the magnetofossils. They were able to find traces of the isotope from approximately 2.2 million years ago, the expected date from a previous study. Bishop's next step is to analyze much greater amounts of sediment, and if they contain Fe-60, he will attempt to use it as a function of time.Nature of Science
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