Reading Ancient Texts With X-Ray Vision

Mount Vesuvius buried the Italian town of Herculaneum under so much volcanic ash and rock in the year 79 that nearly 1,700 years passed before archaeologists discovered its ancient library of papyrus scrolls. Scholars believe these charred, carbonized scrolls conceal a treasure trove of historical and literary works, but the scrolls tend to disintegrate when researchers attempt to unroll and read them. An international team led by Vito Mocella of Italy’s National Research Council and Emmanuel Brun of the European Synchrotron Radiation Facility, in France, have found that X-ray phase-contrast tomography can be used to read what’s on the scrolls without unfurling them (Nat. Commun. 2015, DOI: 10.1038/ncomms6895). Scientists have used X-ray imaging techniques on archaeological finds in the past, but those methods usually rely on differences in the absorbance of materials. The carbonized papyrus and the carbon-based inks of the Herculaneum scrolls are indistinguishable in their absorbance. The materials do, however, differ in their indexes of refraction. Differences in this optical property produce different phase changes in X-rays that penetrate the rolled-up samples and enabled the team to reconstruct written letters. The researchers say this noncontact technique could be extended to any delicate writing sample.