Researchers have long known that a Viking settlement existed in North America centuries before Christopher Columbus was born—and they now have a firm date for it for the first time. Scientists who looked for the impact of a solar storm in tree rings from wood at the Newfoundland site determined that it was inhabited in 1021 AD, exactly 1,000 years ago, the New York Times reports. In a study published in the journal Nature, researchers say they analyzed three wooden items from the L'Anse aux Meadows site that had been cut with metal tools, which Indigenous people in the area didn't use at the time.
The researchers say they looked for evidence of a cosmic ray event that caused elevated levels of radioactive carbon-14 in the atmosphere in 993 AD, and found it was exactly 28 rings before all three pieces of wood had been cut. Study co-author Margot Kuitems says the team searched through artifacts for offcuts —"basically rubbish"—so they could count rings to the bark layer. "If you have an artifact or even a construction beam, often those outer layers are stripped off," she says, per the Smithsonian. Kuitems says previous dates for the settlement were only known through Viking sagas, "oral histories that were only written down in the 13th century, at least 200 years after the events they described took place."
While the study has confirmed a date when the site was occupied, it's not clear whether it was toward the beginning or the end of a Viking occupation believed to have lasted up to 13 years. It's also unclear why the Viking settlers abandoned the settlement in what they called Vinland and returned to Greenland. Sturt Manning, a professor of archaeology at Cornell University, tells NBC that the cosmic ray technique is now being used to establish dates at other historic sites. "It’s a clever application," he says. "This is the first clear evidence of Europeans arriving in North America." (Yale's Vinland map is now believed to be a fake.)
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