The Field acquired its collection of mummies mostly in the late 19th century and started X-raying them around 1910. But it was only recently that the museum was able to virtually “unwrap” the mummies, thanks to a digital CT scanner the museum borrowed from Genesis Medical Imaging. The Field set up the machine, made by GE, in its parking lot and generated more than 60 gigabytes of data in a week by scanning 10 Peruvian and six-and-a-half Egyptian human mummies and a number of goose, gazelle, cat, vulture and falcon mummies. One mummy in a coffin was too big for the machine, so they were only able to scan half of it. “X-rays are great, but they distort the shapes and can hide less dense objects behind more dense objects,” Brown says.
CT and X-ray scanners both rely on radiation to see inside the body. But CT machines use a narrow, rotating beam of X-rays that creates narrow slices of the body a computer can later assemble into detailed 3D images.
CT allowed Brown and his team to make accurate measurements and see everything inside the wrapping. Digital scanners are also fast. They can scan a complete human mummy in about 90 seconds.
Using CT outside the medical industry is not a completely new idea. GE is using souped-up “industrial” CT scanners to inspect jet engine parts. Archeologists in Germany used the machines to study mummies as well an ancient sword stuck in a stone and to decipher a precious scroll.
The mummy scans uncovered one 3,000-year-old fake. Instead of feline remains inside a cat-shaped mummy, scientists found a few bird bones, some leather strips and gravel to give it the correct heft. “It made us question the significance of those empty mummies,” Brown says. “There’s no possible way a buyer wouldn’t know the wrapping was empty, based on weight.” Brown surmised that the empty mummies must have been purchased intentionally, leading him and his colleagues to come up with their theory that those might have been budget buys.
Another interesting find was a collection of items hidden inside some of the mummies. After 3,500 years of mummifying their dead, Egyptians started to run out of burial space. That led to tomb sharing, which created logistics problems. To save room, embalmers began stuffing the dead person’s wrapped organs in the body cavity along with amulets and figurines, rather than placing them around the mummy.
Three millennia later, the frugal solution created problems for Brown and his colleagues. Canopic jars, which originally were placed around the mummies, have lids that identify the organ they contain. But the same objects placed inside the mummy show up as a solid mass on an X-ray.
The CT scanner, on the other hand, picked up the markings on the amulets and figurines, allowing them to be identified. Remarkably, the scans showed small wax figurines in each organ packet in one mummy. Each figure corresponded to a particular organ, so researchers are able to go back and compare the known organs with other mummies’ scans.
“Mummies are enigmatic figures,” Brown says. “But we’ve been able to progressively strip away 20 layers of linen layer by layer. It’s fascinating.”