Beryllium-10 allows researchers to date fossils as much as 10 million years old. Credit: Deposit PhotosShareAn unexpected radioactive discovery beneath the Pacific Ocean seabed may provide researchers with a new global geologic time marker. According to a study published on February 10th in the journal Nature Communications, this previously unknown isotopic accumulation may be the result of cosmic disruptions caused by an ancient, near-Earth supernova.Researchers often use radiocarbon dating to determine the age of many fossilized plant and animal specimensbut the method has its limits. Because carbon-14s half-life is roughly 5,700 years, samples older than 50,000 years lack enough isotopes to detect. Anything beyond that age requires analyzing isotopes such as beryllium-10, whose 1.4-million-year half-life allows researchers to date samples as far back as 10 million years.The problem, however, is that naturally occurring beryllium-10 is a rare find. Isotopes are only created after high-energy cosmic rays interact with the upper atmospheres oxygen and nitrogen. The resulting beryllium-10 radionuclides then eventually fall to Earth in precipitation, where they are subsequently absorbed into the ground.Schematic depiction of production and incorporation of cosmogenic10Be into ferromanganese crusts. Credit: HZDR / blrck.de Global dating archives require a shared geologic event that allows them to synchronize between each other. An event based on beryllium-10 isotopes would allow experts to vastly improve their ability to analyze the planets history. But according to Domink Koll, a physicist at Germanys Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the studys lead author, no such event has been found.For periods spanning millions of years, such cosmogenic time markers do not yet exist, Koll said in a statement.But after analyzing two sets of ferromanganese crust samples collected from Pacific Ocean floor drill sites, Koll and colleagues at the TUD Dresden University of Technology and the Australian National University believe they may now have just such a time marker in a geologic trove of beryllium-10.Their discovery relied on the results of accelerator mass spectrometry. After purifying their ocean floor samples, Kolls team subjected them to high voltages to speed up the movement of individual atoms. These atoms were then rerouted by powerful magnets and recorded using fine-tuned detection equipment. In this case, the final beryllium-10 measurements surprised them.At around 10 million years, we found almost twice as much [beryllium-10] as we had anticipated, explained Koll. We had stumbled upon a previously undiscovered anomaly.To make sure their readings werent the accidental result of contamination, Kolls team retrieved and analyzed more samples taken from additional sites in the Pacific Ocean. Like their first experiments, these newer selections showed similarly high beryllium-10 levels.But what was responsible for this major spike in isotopes? According to Koll, thats still anyones guessalthough two theories appear to be the most plausible. The first is related to shifts in ocean circulation near Antarctica that occurred 10-12 million years ago.This could have caused [beryllium-10] to be unevenly distributed across the Earth for a period of time due to the altered ocean currents, Koll said. Those isotopes may have eventually concentrated in the Pacific Ocean, where physicists eventually recovered them. Get the Popular Science newsletter Breakthroughs, discoveries, and DIY tips sent every weekday. By signing up you agree to our Terms of Service and Privacy Policy.The second theory involves a potential event that began not on Earth, but in deep space. According to the team, cosmic rays generated by a nearby supernova possibly passed through the planets atmosphere around 10 million years ago. This may have caused severe damage to the Earths heliosphere, allowing for more cosmic radiation to interact with oxygen and nitrogen to generate the influx of beryllium-10.To find out if either theory is the true explanation, Koll hopes he and other teams can collaborate and compare additional samples from around the world. Finding similarly elevated beryllium-10 levels in other locations would bolster the supernova hypothesis, while a lack of them may support the more localized ocean current idea.