Age of oldest rocks off by millions of years

Zircon gives clues to the past (Image: Science/AAAS)

Two of the solar system’s best natural timekeepers have been caught misbehaving, suggesting that the accepted ages for the oldest known rock samples are off by a million years or more.

According to two new studies, a radioactive version of the element samarium decays much more quickly than previously thought, and different versions of uranium don’t always appear in the same relative quantities in earthly rocks.

Both elements are used by geologists to date rocks and chart the history of events on our planet and in the solar system.

“If you have a critical event in Earth’s history, something like an extinction event or a climate change shift or a meteorite impact, you need to know the absolute age with the most confidence,” says Joe Hiess of the British Geological Survey, who led one of the studies. “In Earth sciences there’s a need to be able to define what happened first and what happened second.”

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