Researchers have not been given permission to take samples from the mummy, but they also want to preserve her for future examinations.
The mummy traveled to Argonne in a heavy wooden crate, accompanied by form-fitting padding and protective straps. She was placed inside the radiation enclosure of the research room, where the 1/110th-of-an-inch beam, which Stock describes as a "pencil beam," penetrated the materials of the mummy. Stock and Jonathan Almer, a lab technician at Argonne, then looked at the readout from the X-ray detector to examine the structure of the defraction patterns -- the fingerprint of the material hit by the X-ray beam.
By studying the linen wrappings, the skeleton, other matter inside the wrapping and the external portrait, researchers can try to determine what materials were used and where they came from. Identifying and tracing the materials shines light on the culture, trade networks and commerce in the Roman Empire of the late first and early second centuries.
In August, the mummy underwent a CT scan at Northwestern Memorial Hospital. The scan enabled researchers to confirm the mummy girl was about 5 years old, giving researchers a preliminary understanding of the mummy's composition and structure. It also pinpointed specific areas to be studied further with the help of the Argonne equipment.
And because child mummies are unusual, researchers also are hoping the new examination will reveal more about why the girl may have been preserved in such a manner.
The mummy is one of about 100 worldwide with a painted portrait embedded in the wrapping above where the head would be, a style introduced by the Romans. The analysis also will provide clues about Roman-Egyptian mummy portraits, a style that differs from the more familiar Egyptian mummies, which featured three-dimensional sculpture-style faces in an idealized form.
"She's really quite rare," said Essi Ronkko, a curatorial associate at the Block Museum of Art at Northwestern. "You don't get to study a mummy like this often. This is invaluable because it's a fully intact mummy."
Ronkko said she stumbled on the presence of the mummy at the Styberg Library reference room when researching the art museum's upcoming exhibit on mummy portraits. She worked with others at the university to incorporate her into the exhibit and helped launch additional research with Walton, Stock and Taco Terpstra, assistant professor of classics and history.
The mummy is often referred to as the Hibbard mummy and also as Hawara Portrait Mummy No. 4. The mummy made its way to Evanston after it was given to Lydia Beekman Hibbard as a gift for providing financial support to archaeologist Flinders Petrie's excavations in a Roman cemetery in Hawara. She donated the mummy a year later to what was then Western Theological Seminary of Chicago.
Affixing the mummies with a portrait "is a decidedly Roman phenomenon," Walton said. "So being able to study one and find out more about how it was made and used in the Roman period is very important."