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Scientists develop new method for deciphering ancient scrolls
Even a handheld XRF scanner is sufficient to determine most promising scrolls for further analysis.
The Vesuvius Challenge is an ongoing project that combines “digital unwrapping” with crowdsourced machine learning to decipher the so-called Herculaneum scrolls, badly charred 2,000-year-old papyri too fragile to be physically unrolled. The effort just got an additional boost. A team of researchers created their own contemporary model papyrus scrolls—charring them just like the originals—to validate a screening method to determine which of the Herculaneum scrolls were written in lead-based ink and hence are the most promising candidates for further analysis. They described the process in a new paper published in the journal PLoS ONE.
As previously reported, the ancient Roman resort town of Pompeii wasn’t the only city destroyed in the catastrophic 79 AD eruption of Mount Vesuvius. Several other cities in the area, including the wealthy enclave of Herculaneum, were fried by clouds of hot gas, called pyroclastic pulses and flows. But still, some remnants of Roman wealth survived. One palatial residence in Herculaneum—believed to have once belonged to a man named Piso—contained hundreds of priceless written scrolls made from papyrus, singed into carbon by volcanic gas.
The scrolls stayed buried under volcanic mud until they were excavated in the 1700s from a single room that archaeologists believe held the personal working library of an Epicurean philosopher named Philodemus. The few opened fragments helped scholars identify various Greek philosophical texts, including On Nature by Epicurus and several by Philodemus himself, as well as a handful of Latin works. But the more than 600 rolled-up scrolls were so fragile that it was long believed they would never be readable, since even touching them could cause them to crumble.
Brent Searles’ lab at the University of Kentucky has been working on deciphering the Herculaneum scrolls for many years. He employs a different method of “virtually unrolling” damaged scrolls, which he used in 2016 to “open” a scroll found on the western shore of the Dead Sea, revealing the first few verses from the book of Leviticus. The so-called En Gedi scroll was recovered from the ark of an ancient synagogue destroyed by fire around 600 CE. To the naked eye, it resembled a small lump of charcoal, so fragile that there was no safe way to analyze the contents.
The team’s approach combined digital scanning with micro-computed tomography—a noninvasive technique often used for cancer imaging—and segmentation to digitally create pages, augmented with texturing and flattening techniques. Then they developed software (Volume Cartography) to virtually unroll the scroll.
Many of the inks used by Egyptian scribes contained large traces of metals, including lead, making them ideal for X-ray imaging. The older Herculaneum scrolls, however, were written with carbon-based ink (charcoal and water), so one would not get the same fluorescing in the scans; there is almost no difference in X-ray absorption between parts of the papyrus with ink and parts without ink. Searles was still able to capture minute textural differences, training an artificial neural network to do so.
Douglas Seiler, a retired inventor, was working with Berkeley SETI on a new telescope called Panoseti when he heard about the Herculaneum scrolls—as well as the poor signal-to-noise ratios that had been plaguing the efforts of Searles and others to digitally unwrap and decipher them. In 2016, scientists identified letters in two fragments of a scroll that contained lead, suggesting that some of the scrolls might be written in lead-based ink. So Seiler set out to test which of the scrolls were written with lead-based ink and put together an interdisciplinary team to help, including two retired Berkeley chemists and a Berkeley graduate student in archaeology with expertise in ancient Egyptian inks.
The authors purchased modern Egyptian papyrus, which