How was the necropolis found?

A team of scientists turned to cosmic rays for help – specifically an imaging technique called muography or muon tomography – and discovered a previously unknown underground burial chamber.

Science has a long history of using muons to visualize archaeological structures. Nowadays this process has become easier because cosmic rays provide a constant supply of these particles and we are good at detecting them.

• In the 1950s, this approach was used to measure a tunnel in Australia.
• Nobel Prize-winning physicist Luis Alvarez put muon imaging on the map when he teamed up with Egyptian archaeologists to find hidden chambers in Khafre’s pyramid at Giza.
• Muons are also used at border crossings to search for fugitive nuclear material and to monitor active volcanoes in hopes of detecting when they might erupt.
• In 2008, scientists at the University of Texas at Austin tried to reuse ancient muon detectors to search for possible hidden Mayan remains in Belize.
• And physicists at Los Alamos National Laboratory are developing portable versions of muon imaging systems to unlock the secrets of the dome structure on the Cattedrale di Santa Maria del Fiore in Florence, Italy. In this way, they hope to determine how they will carry out its reconstruction.

How does muon technology work?

There are many types of muon imaging, but all of them usually involve chambers filled with gas. As the muons pass through the gas, they collide with the gas’s particles and emit a flash of light recorded by the detector, allowing scientists to calculate the particle’s energy and trajectory.

It is similar to X-ray imaging or ground radar, except that natural high-energy muons are used instead of X-rays or radio waves. This higher energy provides images of thick, dense matter such as the stones used to build the pyramids.

The denser the object, the more muons are blocked and create a noticeable shadow. Hidden cameras will appear in the final image as they block fewer particles.

Necropolis in Naples

The necropolis in the current site of Sanita was used for burials from the end of the 4th century BC to the beginning of the 1st century AD. Over time, the site was covered with sedimentary rocks due to a series of natural disasters, especially mud and stones moving from the hills during heavy rains.

The exact size of the necropolis is unknown, but probably contained dozens of tombs, each containing several bodies. Four other tombs, now known as Ipogeo dei Cristallini, were discovered at the end of the 19th century under the di Donato family palace on Via Cristallini. After the 1980 earthquake, two more burial chambers were discovered: Ipogeo dei Togati and Ipogeo dei Melograni. They are all similar in structure.

This collage shows other burial chambers similar in structure to the one found in Naples. In picture b – Ipogeo dei Melograni. Open c – Ipogeo dei Togati. The latter was described by archaeologist Michele Ruggero in 1888 / Photograph: V. Tioukov

These discoveries gave rise to hopes of finding even more hidden burial chambers. Researchers from the University of Naples Federico II, the National Institute of Nuclear Physics in Naples, and the University of Nagoya in Japan thought muography would be an excellent tool for this.

Due to its non-invasive nature, this method is particularly suitable for urban environments where active exploration methods such as seismic waves or boreholes are not possible.
– tell the authors.

It is not yet clear whether further excavations will be carried out.