Shroud of Turin: Tests May Give It an Age

Seven research institutions around the world, including three in the United States, will participate in an unprecedented project next year that should precisely date the Shroud of Turin and possibly end a centuries-old controversy.

The shroud, which many believe to have been the burial cloth for Jesus Christ, shows the image of a man who died by crucifixion.

In 1978, the shroud was the subject of a wide range of scientific studies, many of them based on chemical analyses. But those studies, designed merely to determine the authenticity of the image, failed to turn up evidence that would disprove the authenticity.

And until now, the Vatican has resisted pressure to determine the age of the shroud through radiocarbon dating because the technique would have destroyed much of the shroud. But that danger has been lessened with the development of new techniques that can yield reliable results from only a tiny fragment of the shroud.

Tests Results Long Awaited

The test, long awaited by scientists and religious leaders alike, could prove that the artifact is far too young to have been the burial cloth.

However, even if the results show that the shroud dates back to the time of Christ, it will not prove that it was indeed the burial cloth, or that the image on the 14-feet-by-4-feet piece of linen is that of Jesus.

Thus, seven labs are in the position of being able to prove a negative, but not a positive. The results are expected to be announced in early 1988.

“What will come out of our effort will be the age of the cloth,” said Douglas Donahue, a nuclear physicist at the University of Arizona, one of the participating institutions.

The others are Oxford, Rochester (N.Y.) and Zurich universities, and the Centre pour Faibles Radioactivites in France, Harwell in the United Kingdom and the Brookhaven National Laboratory in New York.

Until a few years ago, even radiocarbon techniques would have destroyed much of the shroud because samples to be dated must first be burned so that the carbon can be extracted. And that required large samples in order to determine the ratio between carbon 14 and other carbon isotopes, one of nature’s most reliable time clocks.

But a new technology has evolved, using a nuclear accelerator to bombard a sample with a beam of cesium ions, giving the carbon atoms a negative charge so that they can be collected with an electric field. The carbon atoms are then fired through the accelerator and into a target of argon atoms. That gives the carbon 14 atoms a positive charge so that they can be drawn off with a magnet from the other negatively charged carbon isotopes.

Device Counts Isotopes

The magnet diverts the carbon 14 isotopes to a device that counts them.

In nature, carbon 14 is created when nitrogen atoms in the atmosphere are struck by cosmic rays from outer space. The carbon 14 becomes part of the carbon dioxide in the atmosphere, which is taken up by all living things.

As long as the animal or plant remains alive, the percentage of carbon 14 in its tissues remains constant, but upon death it no longer takes up carbon dioxide, and the various types of carbon isotopes decay at different rates. Thus the percentage of carbon 14 reveals the time at which the plant or animal ceased taking up carbon dioxide.

The Shroud of Turin is made of linen, and the ratio of carbon 14 to carbon 12 and 13--which are carbon atoms of a different weight, called isotopes--will tell scientists when the plant fibers were turned into cloth.

The task will be especially difficult because only about one out of every trillion carbon isotopes is carbon 14.

Finding a Marble

“It’s like if you had an acre of blue marbles, three feet deep, with one red marble mixed in with the blues,” said Paul E. Damon, a University of Arizona geochemist and principal co-investigator with the university’s Laboratory of Isotope Geochemistry. “Your job would be to find the red marble.”

The University of Arizona’s accelerator was completed in February of 1982, and it immediately proved its value by showing that two skulls found in California were far younger than scientists had believed, thus saving anthropologists the trouble of trying to explain how humans could have been in California 30,000 years before Homo sapiens appeared in the Old World.

After that, scientists at Arizona and elsewhere began seeking permission from the Vatican to date the Shroud of Turin.

The British Museum last spring sent out 18 linen samples of known age to labs that had expressed an interest in dating the shroud. Seventeen of the 18 results were on the money, Damon said. The 18th sample, tested by a Zurich university, apparently had been contaminated, he added.

Vatican Agreement Seen

The impressive results led the the Pontifical Academy of Sciences to agree to the test. The Vatican, which has custody of the shroud, still has not given the effort its blessing, but Damon believes that it is only a formality.

“The Pontifical Academy would not have gone this far if it didn’t have the backing of the Vatican,” he said. “Their feeling is the time has come to date the shroud.”

When the time comes, either Damon or Donahue will go to the Cathedral of St. John the Baptist in the northwestern Italian city of Turin, where the shroud is kept, to witness samples being taken.

The samples will be snipped from an “unobtrusive” area that does not include the image or bloodstains that many believe came from Christ’s crown of thorns and various wounds from the Crucifixion, Donahue said.

After placing the samples in sealed envelopes, the British Museum will add other envelopes containing dummy samples of known age, and all the envelopes will be dispatched to the various labs. None of the labs will know which envelopes contain the samples from the shroud.

‘One or Two Dummies’

“We will get at least one or two dummies” for the test, Damon said.

The test results will be turned over to the Pontifical Academy, which is to make them public around Easter of 1988. The labs will also publish their findings some time later.

If it turns out that the shroud does date back to the time of Christ, it will not prove that the image is that of Jesus, but it will be a vital tool in the hands of those who already believe that the faint image of a bearded man is that of Jesus, mysteriously transferred to a piece of linen.

The known history of the shroud dates back to the Middle Ages, and even then it was engulfed in controversy. Fearful that the shroud might turn out to be a hoax, the Catholic Church had it removed from public view, and it has been seen rarely since. The Vatican has never said it believes that the shroud was the burial cloth of Jesus.

In the fall of 1978, a team of scientists was allowed to conduct extensive tests of the shroud while it was on display in the Turin cathedral. Although conditions there were less than ideal for many of the experiments, the scientists felt that they could rule out the notion that the image of the man was painted on the cloth because microscopic examination did not show any brush marks and because no paint pigments could be found.

No ‘Human Chicanery’

“For now, we know that the shroud was not a product of any human chicanery,” two members of that team, Samuel Pellicori and Mark S. Evans, wrote in the January, 1981, issue of Archeology magazine.

“But was it the actual burial cloth of Christ?” they continued. “Our research has not been able to prove that weighty conclusion, nor perhaps will science ever be able to say. But at the same time, some of the most exhaustive research ever conducted on any relic, object of art or archeological artifact in no way has eliminated that possibility.”

If, however, it turns out that the shroud dates back only to the Middle Ages, “that will put a wet blanket on it,” Donahue added.