GRONINGEN, THE NETHERLANDS—According to an NBC News report, researchers led by Margot Kuitems of the University of Groningen used a cosmic ray event in A.D. 993 to date the Viking settlement at L’Anse aux Meadows to A.D. 1021. First, Kuitems and her colleagues identified three pieces of wood at the site that had been cut with metal tools, which were used by the Norse but not the Indigenous people who also lived in the region. Then, they looked for a spike in radioactive carbon in the wood marking the cosmic ray event. Finally, microscopic analysis of growth rings laid down by the trees after A.D. 993 out to the tree’s outer bark revealed when it had been cut down. The study indicates that all three pieces of wood came from trees felled in A.D. 1021. “Previously the date was based only on sagas—oral histories that were only written down in the thirteenth century, at least 200 years after the events they described took place,” Kuitems said. The explorers may have collected some of the wood found at the site from warmer regions to the south, she added. For more on the Vikings, go to "Largest Viking DNA Study," one of ARCHAEOLOGY's Top 10 Discoveries of 2020.