Image courtesy of © Marco Samadelli via ScienceDaily. Click to enlarge.

When Oetzi the Iceman was found jutting out of a melting glacier in the Ötztal Alps on September 19, 1991, his discoverers, Erika and Helmut Simon, immediately noticed his tattoos—which, at more than 5000 years old, are some of the oldest documented tattoos in the world. Previous studies had analyzed and itemized the tats, but now, using a new, non-invasive technique he invented, Marco Samadelli, a scientist at the EURAC-Institute for Mummies and the Iceman in Italy, has mapped all of the mummy's tattoos for the first time—and discovered a previously unknown tattoo. The method and results of his study were published in Journal of Cultural Heritage.

Samadelli photographed Oetzi from various angles in the mummy's refrigerated cell at the South Tyrol Museum of Archaeology using a multi-spectral camera. "Each shot was taken seven times, using a different wavelength each time," Samadelli said in a press release. "This enabled us to cover the different depths at which the carbon powder used for the tattoos had been deposited. The ultraviolet waves were adequate for the upper skin layers, whilst we resorted to infrared light for the lower layers."

The different wavelengths revealed tattoos deep in the skin and invisible to the human eye. Oetzi has 61 markings, which consist mostly of parallel lines in groups of two, three, or four between 0.7 and 4 centimeters long. (There are also two crosses.) The newly discovered ink, located on Oetzi's rib cage, wasn't noticed earlier because the mummy's skin had darkened so much.

Because most of the mummy's tattoos are located on the lower back and along the leg between the knee and the foot, researchers had speculated that perhaps the markings were used as part of some kind of treatment—maybe an early form of acupuncture—while others believe that the markings might have symbolic or religious significance. Oetzi's rib tattoo will undoubtedly give the researchers more to consider.