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Method would “revolutionize” dating of ancient treasures

March 23, 2010
Courtesy of the American Chemical Society
and World Science staff

Sci­en­tists say they have found a way to es­ti­mate the ages of an­cient mum­mies, art­work, and oth­er relics with­out dam­ag­ing these trea­sures, as stand­ard cur­rent mea­sure­ments do.

The bas­ic mod­ern tech­nique for dat­ing ar­ti­facts is called ra­di­o­car­bon dat­ing and re­quires the burn­ing of a ti­ny piece of the ob­ject at hand. The new meth­od is a var­i­ant of the same tech­nique, but in­stead in­volves sub­ject­ing the ob­ject sur­face to a gen­tle chem­i­cal re­ac­tion that causes no ap­pre­ci­a­ble dam­age, ac­cord­ing to de­ve­lop­ers of the tech­nique.

The "Venus of Bras­sem­pouy," a ti­ny ivo­ry fig­ur­ine, is among ar­ti­facts sci­en­tists say they could an­a­lyze with a new meth­od for de­ter­min­ing the age of an ob­ject with­out dam­ag­ing it. (Cred­it: Wiki­me­dia Com­mons)
It will take time and ad­di­tion­al da­ta to con­vince the cu­ra­tors of price­less ar­ti­facts of the val­id­ity of these claims, the de­vel­op­ers ac­knowl­edged. But de­scrib­ing the new meth­od at the an­nual meet­ing of the Amer­i­can Chem­i­cal So­ci­e­ty on March 23 in San Fran­cis­co, they said it could al­low sci­en­tif­ic anal­y­sis of hun­dreds of ar­ti­facts off lim­its be­fore now due to con­cerns about dam­age.

“This tech­nique stands to rev­o­lu­tion­ize ra­di­o­car­bon dat­ing,” said Mar­vin Rowe of Tex­as A&M Uni­vers­ity, who led the re­search team. “In the­o­ry, it could even be used to date the Shroud of Tur­in,” a centuries-old fab­ric be­lieved by some Chris­tians to bear the im­age of the cru­ci­fied Je­sus.

In ra­di­o­car­bon dat­ing, an ob­ject’s age is es­ti­mated based on its con­tent of naturally-occurring ra­di­o­ac­t­ive car­bon. Or­gan­ic ma­te­ri­als con­tain an amount of this car­bon that de­pends on how long ago or an­i­mal from which they come has died.

Tra­di­tion­al car­bon dat­ing in­volves re­mov­ing and burn­ing a small bit of the ob­ject – pos­sibly a ti­ny amount, but still too much for some ar­ti­facts and those who care for them.

In Rowe’s meth­od, called “non-destructive car­bon dat­ing,” sci­en­tists put an ar­ti­fact in a spe­cial cham­ber with a plas­ma, an elec­tric­ally charged gas si­m­i­lar to gas­es used in big-screen plas­ma tel­e­vi­sion dis­plays. The gas slowly makes the sur­face of the ob­ject un­dergo a re­ac­tion called oxid­ation, which pro­duces car­bon di­ox­ide. The car­bon di­ox­ide can then be an­a­lyzed for its con­tent of ra­di­o­ac­t­ive car­bon with­out dam­ag­ing the sur­face, he said.

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.

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 said.

The sci­en­tists are re­fin­ing the tech­nique. Rowe hopes to use it to an­a­lyze ob­jects such as a small ivo­ry fig­ur­ine called the Venus of Brassem­pouy, thought to be about 25,000 years old and one of the ear­li­est known de­pic­tions of a hu­man face.

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Scientists say they have found a new way to estimate the age of ancient mummies, artwork, and other relics without damaging these treasures, as standard current measurements do. The basic modern technique for dating artifacts is called radiocarbon dating and requires the burning of a tiny piece of the object at hand. The new method is a variant of the same technique, but instead involves subjecting the object surface to a gentle chemical reaction that causes no appreciable damage, according to proponents of the new technique. It will take time and additional data to convince the curators of priceless artifacts of the validity of these claims, the developers acknowledged. But describing the new method at the national Meeting of the American Chemical Society on March 23 in San Francisco, they said it could allow scientific analysis of hundreds of artifacts off limits before now due to concerns about damage. “This technique stands to revolutionize radiocarbon dating,” said Marvin Rowe of Texas A&M University, who led the research team. “In theory, it could even be used to date the Shroud of Turin,” a centuries-old fabric believed by some Christians to bear the image of the crucified Jesus. In radiocarbon dating, an object’s age is estimated based on its content of naturally-occurring radioactive carbon. Organic materials contain an amount of this carbon that depends on how long ago or animal from which they come has died. Traditional carbon dating involves removing and burning a small bit of the object – possibly a tiny amount, but still too much for some artifacts and those who care for them. In Rowe’s method, called “non-destructive carbon dating,” scientists put an artifact in a special chamber with a plasma, an electrically charged gas similar to gases used in big-screen plasma television displays. The gas slowly and gently makes the surface of the object undergo a chemical reaction that produces carbon dioxide. The carbon dioxide can then be analyzed for its content of radioactive carbon without damaging the surface, he said. 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. 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 said. The scientists are refining the technique. Rowe hopes to use it to analyze objects such as a small ivory figurine called the “Venus of Brassempouy,” thought to be about 25,000 years old and one of the earliest known depictions of a human face.