How to date ancient treasures without damaging them

Physics Today : A new radiocarbon dating technique that can determine the age of ancient mummies, old artwork, and other relics without causing damage was announced yesterday at the annual meeting of the American Chemical Society held in San Francisco, California."This technique stands to revolutionize radiocarbon dating ,” said Marvin Rowe , of Texas A&M university at Qatar, who led the research team. “It expands the possibility for analyzing extensive museum collections that have previously been off limits because of their rarity or intrinsic value and the destructive nature of the current method of radiocarbon dating.” Traditional carbon dating involves removing and burning small samples of the object.Although it sometimes requires taking minute samples of an object, even that damage may be unacceptable for some artifacts. The new method does not involve removing a sample of the object.Conventional carbon dating estimates the age of an artifact based on its content of carbon-14 ( ¹⁴C), a naturally occurring, radioactive form of carbon. Comparing the ¹⁴C levels in the object to levels of ¹⁴C expected in the atmosphere for a particular historic period allows scientists to estimate the age of an artifact.Both the conventional and new carbon dating methods can determine the age of objects as far back as 45,000 to 50,000 years, Rowe said.In conventional dating methods, scientists remove a small sample from an object, such as a cloth or bone fragment. Then they treat the sample with a strong acid and a strong base and finally burn the sample in a small glass chamber to produce carbon dioxide gas to analyze its C-14 content.Rowe’s new method eliminates sampling by placing the entire artifact in a special chamber with a plasma. The gas slowly and gently oxidizes the surface of the object to produce carbon dioxide for ¹⁴C analysis without damaging the surface, he said.Rowe and his colleagues used the technique to analyze the ages of about 20 different organic substances, including wood, charcoal, leather, rabbit hair, a bone with mummified flesh attached, and a 1,350-year-old Egyptian weaving. The results match those of conventional carbon dating techniques, they say.The chamber could be sized to accommodate large objects, such as works of art.However, Rowe acknowledged that it would take a significant amount of data to convince museum directors, art conservators, and others that the new method causes no damage to such priceless objects.Paul Guinnessy Related Link Non-destructive 14C dating: Plasma-chemistry and supercritical fluid extraction