Let’s start, once is not custom, with information sixty years old but which, although capital, may still have escaped some: Christopher Columbus is not the first European to have set foot in America. About half a millennium before the famous crossing of the Atlantic made by the Genoese navigator in 1492, Vikings had landed on the Canadian island of Newfoundland, in a place today called Anse aux Meadows. They had also lived there, as evidenced by excavations carried out in the 1960s, which brought to light the remains of peat and timber-frame buildings – dwellings, forges, workshops – such as the Scandinavians built in Greenland and in Iceland. Registered since 1978 on the UNESCO World Heritage List, Anse aux Meadows is a major archaeological site, further testimony to the Viking expansion in the Middle Ages.
An important question remained about this American occupation: when did it date exactly? The consensus evoked the turning point of the Iis et du IIe millennium AD, based on analysis of architectural remains and a handful of objects, as well as Nordic sagas, accounts established long after the supposed facts. The dating of about fifty remains had been attempted in the past without giving precise results given the limitations and uncertainties of this technique in the 1960s and 1970s: the estimates stretched from the end of the 8th century.e century in the middle of the eleventhe. In this unclear context, the result of an international study published on Wednesday, October 20 in Nature has the effect of a bomb, both in its precision and in the year that is mentioned: it shows that the Vikings were present at Anse aux Meadows in 1021, exactly a thousand years ago! However, that doesn’t say when they got there or how long they stayed.
“Chronological anchor”
How did these researchers proceed? How did we manage to go from very vague to very sharp? It took a helping hand from the sky … In this case, the scientists took advantage of an unknown astrophysical event – solar flare, supernova? – which, in 993, caused an influx of cosmic rays on Earth. Arriving in the atmosphere, these very energetic particles cause cascades of reactions with the atoms of the air. And in particular a transmutation of nitrogen into carbon 14. This then experiences a production peak which, as the Japanese researcher Fusa Miyake demonstrated in 2012 by studying Japanese cedars, can be found in annual growth rings. trees. Therefore, if one is lucky enough to have wood that has been cut after a cosmic ray event, the tree ring produced that year will contain much more carbon-14 than its neighbors.
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