Hundreds of papyrus scrolls, reduced to lumps of coal by the 750-degree Fahrenheit cloud that wrapped the ancient Roman city of Herculaneum during the Mount Vesuvius eruption in 79 A.D., might soon emerge as the most significant rediscovery of classical literature since the Renaissance.
Using a powerful X-ray procedure, Italian researchers have been able to read letters hidden inside two carbonized papyri without unrolling them.
"It's the first time a technology achieves such a result," Vito Mocella, a physicist from the National Research Council's Institute for Microelectronics and Microsystems (CNR-IMM) in Naples, told Discovery News. "Until now, imaging techniques have been unable to view the carbon-based ink of these papyri, even when they could penetrate the different layers of their spiral structure."
The scrolls used by Mocella's team were excavated 260 years ago from the Villa of the Papyri in Herculaneum, a magnificent seafront estate perhaps owned by Lucius Calpurnius Piso, Julius Caesar's father-in-law.
The villa housed one of the finest libraries of antiquity. Consisting mainly of Epicurean philosophical texts, the scrolls were carefully stored in shelves covering the walls.
During the devastating eruption of Mount Vesuvius, the scrolls, as well as the Herculaneum citizens, were burned by a furnace-like blast of hot gas.
Paradoxically preserved forever (Herculaneum's seaside air would have destroyed them) the scrolls are now stored at the National Library of Naples. They make up the only library known to have survived the ancient world. The carbonized scrolls are thought to hold Aristotle's lost 30 dialogues, philosophical work by Epicurus, erotic poems by Philodemus, Virgilius's lost eclogue, scientific work by Archimedes and lesbian poetry by Sappho.
Out of the 1,785 scrolls discovered during the 18th century excavation, only 585 had been completely unrolled using a 18th century mechanical method, while 209 have been partly unrolled.
About 400 have never been unrolled and 450 are so difficult to read that their text remains unknown.
"These carbonized papyri are extremely fragile and are inevitably damaged or destroyed in the process of trying to open them to read their contents," Mocella and colleagues wrote in the journal Nature Communications.
Any attempt using non invasive procedures to read the scroll, including multi-spectral technology, have proven ineffective.
The ink used to write the texts was the main barrier.
"Multi-spectral imaging has improved the readability of these texts considerably, but unfortunately it is not applicable to texts that remain rolled-up," Mocella said.
"In antiquity, papyri were written using a black carbon-based ink obtained from smoke residues, the density of which is almost the same as that of the carbonized papyrus," the researchers wrote.
Until now, therefore, it has appeared impossible to distinguish ink from papyrus inside a scroll using conventional X-ray techniques.
To overcome the problem, Mocella and colleagues turned to X-ray phase contrast tomography (XPCT), a 3-D X-ray imaging technique most commonly used in medicine.
The technology takes advantage of subtle differences in the way X-rays pass through different substances, in this case papyrus and ink.
"Papyrus writing material consisted of two layers, whose fibers ran perpendicular to one another; the scribe would usually write the text in vertical columns on the side of the papyrus sheet where the horizontal fibers were uppermost," the researchers wrote.
They noted that carbon-based ink did not penetrate into the papyrus fibers, but sat atop them, producing a slight thickness on the surface.
"As we shall see, this fact proved to be crucial for our experiments," Mocella said. "Once amplified by phase contrast technique, that relief, about some 100 micron thick, made it possible to read some letters."
Using the technology at the European Synchrotron Radiation Facility in Grenoble, France, the team examined two scrolls -- one unrolled and the other still rolled-up -- which were handed to Napoleon Bonaparte as a gift in 1802 and now belong to the collection of the Institut de France.
On the unrolled scroll the researchers identified two words written in several superposed layers of papyrus. On one of the hidden layers, the sequence of Greek capital letters PIPTOIE, possibly meaning "would fall," could be read, while another sequence, EIPOI, meaning "would say," was spotted in the following line.
But the main object in Mocella's investigation was a carbonized, sausage-shaped rolled-up papyrus.
"The tremendous pressure of the pyroclastic material compressed the scroll and deformed its internal spiral structure, the layers of which are folded in a nearly chaotic and badly entangled fashion," the researchers said.
The letters were likely distorted, making data analysis a real challenge.
Nevertheless, the scanner was able to pick out all 24 letters of the Greek alphabet. The researchers not only identified some words such as "deny," "for," "the" and "to move," but also pinpointed a specific handwriting style, which led to the likely author, the Greek philosopher and poet Philodemus.
"While our ﬁrst experiments have revealed only small segments of writing and are in need of further reﬁnement, we note that once the XPCT technique has been tuned, the imaging of an entire papyrus scroll should not require more than a few hours of synchrotron beam time," Mocella said.
New experiments are scheduled for the spring, he said. The researchers also hope to determine the chemical composition of the ink.
According to ancient sources it was made of water, smoke residues and gum acacia. Finding the right composition will be crucial to calibrate the beam's energy.
"The impact of our discovery that XPCT can read writing inside carbonized papyrus rolls reaches far beyond the study of one particular Herculaneum papyrus," Mocella and colleagues wrote.
"It holds out the promise that many philosophical works from the library of the Villa of Papyri, the contents of which have so far remained unknown, may in future be deciphered without damaging the papyrus in any way," they said.