The Shroud of Turin, the controversial piece of linen that some believe to be the burial cloth of Jesus Christ, could finally be dated accurately.
A new method "stands to revolutionize radiocarbon dating," according to research presented on Tuesday at the national meeting of the American Chemical Society in San Francisco.
Called "non-destructive carbon dating," the method basically avoids the removal of a sample of the object.
"It expands the possibility for analyzing museum collections that have previously been off limits because of their rarity or intrinsic value," said Marvin Rowe, professor emeritus at Texas A&M University College Station.
Conventional carbon dating estimates the age of an artifact based on the decay rate of the radioactive isotope carbon-14, a variant of carbon that is incorporated in all living organisms.
Any material of plant or animal origin, including textiles, wood, bones and leather, can be dated by its content of carbon-14. Scientists typically remove a small sample from an object, treat the sample with a strong acid and a strong base, and then burn it in a small glass chamber to produce carbon dioxide gas.
Comparing the carbon-14 levels in the object to those expected in the atmosphere for a particular period in history allows scientists to estimate the age of an artifact.
Rowe's new method eliminates the destructive steps of sampling, acid-base washes and burning. The object is simply placed in a special chamber with a plasma, an electrically charged gas similar to that used in big-screen plasma television displays. The gas slowly and gently oxidizes the surface of the object without damaging it to produce carbon dioxide for carbon-14 analysis.
"In the case of the Shroud of Turin, we would roll the cloth into as tight a package as we can make it," Rowe said.
The Turin shroud already underwent carbon-14 dating in 1988. At that time, three reputable laboratories in Oxford, Zurich and Tucson, Ariz., concluded that the cloth on which the smudged outline of the body of a man is indelibly impressed was a medieval fake dating from between 1260 and 1390, and not the burial cloth wrapped around the body of Christ.
However, the radiocarbon dating did not prevent many scholars from formulating various hypotheses questioning the validity of the carbon-14 tests, including the possibility that they were conducted on a sample taken from a medieval patch.
Rowe's method could finally put aside such speculation since it could place the date for the entire shroud.
So far, Rowe and his colleagues have used the technique to estimate 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.
They conceded, however, that it would take a significant amount of data to convince museum directors, art conservators and possibly the Vatican that the non-invasive method indeed causes no damage.
Kept rolled up in a silver casket, the Turin linen has survived several blazes since its existence was first recorded in France in 1357. Most recently, it weathered a mysterious fire at Turin Cathedral in 1997.
It has been on display only five times in the past century. When it last was available to the public in 2000, more than 3 million people saw it. The next viewing will be from April 10 to May 23 in the Turin Cathedral.
