One morning in 79 A.D., the people of the Roman city of Pompeii heard a rumble from Mount Vesuvius, which loomed over them. There had been frequent earthquakes all summer long, so most people weren’t that concerned. Little did they know that the quakes were a warning sign from Vesuvius—which was no ordinary mountain. It was a volcano, and it was about to blow its top. 

Vesuvius erupted with a force more powerful than an atomic bomb. Super-hot gas, ash, and rocks shot 32 kilometers (20 miles) into the sky. The cloud collapsed, sending a wave of hot gas and rock, called a pyroclastic flow, racing toward the city at a speed of more than 160 km (100 mi) per hour. The flow quickly buried the entire city and many of its inhabitants.

Pompeii, which is located near present-day Naples, Italy, was uncovered in 1748. Since then, archaeologists have been slowly excavating the site. 

So far, they’ve dug up the ruins of more than 1,000 buildings. Their work has revealed much about the daily lives of Pompeii’s people: They ate at fast-food stalls, scrawled graffitied schedules of future gladiator fights on walls, and had indoor plumbing.  

In September 2015, a team of scientists from around the world began a new investigation of Pompeii’s victims using medical-imaging machines called CT scanners. These scanners use X-rays, a type of electromagnetic radiation, to take a series of images of all of a body’s internal structures. Computers then stitch these images together to create a 3-D picture (see Inside a CT Scanner). 

The Pompeii team wanted to use the scanners to image the skeletons hidden inside the casts. “The history of a person’s life is embedded in their bones,” says Estelle Lazer, a forensic anthropologist (a scientist who studies skeletal remains) on the team from the University of Sydney, in Australia. By looking at specific parts of the skeleton, such as the jaw and pelvic bones, scientists can tell the person’s gender. The stage of tooth development and the length of certain bones can show how old the person was when he or she died. The bones and teeth can also show evidence of disease and fractures from injuries, which give clues about the person’s health at the time of death. 

The scientists set up a CT scanning lab onsite in Pompeii. There, they put dozens of casts through the machine to see what was inside. The study is still under way, but already the group has uncovered some surprises. 

Experts had long thought that the victims preserved in Pompeii were very old, very young, or sick—in other words, those who couldn’t escape the eruption. But CT scans revealed that the skeletons belonged to people of all ages. For example, one victim nicknamed “The Beggar,” thought to have been an old man, was actually much younger. That suggests that most of Pompeii’s citizens, regardless of their age, didn’t survive the disaster. 

The scans also showed that many people in Pompeii had healthy teeth, despite their lack of modern dental care. The scientists think this may have been due to a diet low in sugar as well as the presence of fluorine—a chemical element that fights tooth decay—in the water around Vesuvius.