Researchers have found an unexpected radioactive isotope, Beryllium-10, at the bottom of the Pacific Ocean. The finding might provide a new global 'time marker', ultimately improving geological dating methods. 

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Beryllium-10 is a rare radioactive isotope and is formed in the Earth's atmosphere mainly by cosmic ray spallation of nitrogen and oxygen. It provides valuable insights into the Earth's geological history. 

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In a study published on February 10 in the journal Nature Communications, the researchers said that this previously unknown isotopic accumulation may be the result of cosmic disruptions. 

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They added that it dates back to around 10 million years ago, and was caused by an ancient, near-Earth supernova. 

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The study was conducted by a research team from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), in collaboration with the TUD Dresden University of Technology and the Australian National University (ANU). 

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Radiocarbon dating is frequently used by researchers to establish the age of several fossilised plant and animal specimens. Since carbon has a half-life of about 5,700 years, it is impossible to detect isotopes in samples older than 50,000 years. 

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Hence, analysis of isotopes like beryllium-10, whose 1.4 million-year half-life enables scientists to date samples as far back as 10 million years, is necessary for anything older than that. 

"However, the radiocarbon method is limited to dating samples no more than 50,000 years old," explains HZDR physicist Dr Dominik Koll. as quoted by phys.org. 

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"To date older samples, we need to use other isotopes, such as cosmogenic beryllium-10 (10Be)," Koll added. 

(With inputs from agencies)