Space might officially be the last frontier, but anyone who has been paying attention knows that there are just as many – if not more – mysteries lurking beneath the surface of our own home planet.

Recently, scientists have discovered a huge “anomaly” under the Pacific Ocean – but what is it?

Technically, an “unexpected” accumulation of beryllium-10, a radioactive isotope.

The international research team published their findings in Nature Communications. In it, they claim the anomaly dates back to a time when ocean currents shifted or cosmic rays interacted with our atmosphere – around 10 million years ago.

Beryllium-10 is produced by oxygen and nitrogen atoms in the Earth’s upper atmosphere interaction with high-energy protons. They believe this timeline could help “serve as an independent marker for marine archives,” allowing scientists to better study how the Earth’s crust has evolved over millions of years.

Researchers looking to date archaeological and geological samples use radioactive isotopes, like in radiocarbon dating. With radiocarbon dating, though, the samples have to be less than 50,000 years old. Older samples require the use of isotopes like beryllium-10.

The half-life of beryllium-10 is 1.4 million years. It breaks down into boron, and allows us to date up to 10 million years back in time.

Researchers in this study examined the boron isotopes using accelerator mass spectrometry, and got some surprising results.

“At around 10 million years, we found almost twice as much [boron-10 isotope] as we had anticipated. We had stumbled upon a previously undiscovered anomaly.”

They believe a “grand reorganization” of ocean currents around the time, leading to larger deposits of beryllium-10. Alternatively, it could have resulted from a celestial event like a “near-Earth supernova” intensifying cosmic radiation.

“Only new measurements can indicate whether the beryllium anomaly was cased by changes in ocean currents or has astrophysical reasons. That is why we plan to analyze more samples in the future and hope that other research groups will do the same.”

The more we are able to understand about Earth’s past, and what events shaped our current reality, the more likely we’ll be able to understand events that could happen in the future.

If you thought that was interesting, you might like to read about why we should be worried about the leak in the bottom of the ocean.