New Israeli Study Demonstrates Exciting Way to Map Subterranean Spaces

Today, archaeology is synonymous with excavation based on a combination of knowledge and educated guesswork. The need to dig deep into the ground just to uncover where to find out more about the treasures and lives of the past is seen as a given. But this may be about to change.

According to a new study published in the Journal of Applied Physics, a multidisciplinary Israeli team has now deployed a detection system based on muons, elementary particles similar to heavy electrons, to scan for underground hollows in Jerusalem.

These findings, reported by The Times of Israel, could equip archeologists worldwide with a powerful new tool to map subterranean spaces before a single shovel is used. 

Innovative Research That ‘X-rays’ Hidden Underground Layers
A member of the research team, Professor Oded Lipschits of Tel Aviv University’s (TAU) Department of Archeology and Ancient Near Eastern Cultures,” told The Times of Israel that the study planned to show that “archeologists can arrive at a site already knowing the underground layout and decide where to dig accordingly.”

According to the study, researchers aimed to develop a simple, low-cost method of producing a 3D map of what lies beneath the bedrock. 

To do this, the scientists used a penetrating but non-invasive muon-powered  imaging technique to probe density distribution at Jeremiah’s Cistern in Jerusalem’s City of David site, just beyond this ancient hub’s Old City walls. This site preserves layers of this ancient city’s past, from the First Temple period of the Iron Age (1200-586 BCE), to the Roman era and then the Early Islamic period. 

By measuring the rate and direction of muons that pass through a target volume using several tracking detectors, a tomographic image (a detailed cross section or slice image) of the internal structure can be reconstructed. The new muon detectors that were used  are a portable and practical adaptation of technology that has previously been used to scan Egypt’s pyramids. 

According to Lipschits, as well as confirming underground cavities already known to archeologists, the researchers revealed previously undiscovered ones.

Unlike X-rays, muons can traverse tens to hundreds of metres of rock or concrete, making them perfect probes for dense or inaccessible structures , as indicated in image in the following post:

This study is part of a trend seeing Israeli archaeology embracing science and tech-led techniques to discover more about the past in a non-invasive way.

These include aerial and remote sensing using drones for broad landscape surveys,  and archaeobotany, the analysis of ancient pollen and other plant remains to reconstruct ancient environments. A Ynet article covers Israel’s sole particle accelerator for carbon-14 separation at the Weizmann Institute of Science to provide insights into the distant and recent past of Israel and its inhabitants.

 A Local Discovery That Will Boost Archeology Worldwide
“All archaeological sites are like Swiss cheese,” Professor Oded Lipschits told The Times of Israel. What diverse sites like the Mayan cities of South America, the pyramids of Egypt, and the site in Jerusalem share is that ancient inhabitants carved out underground spaces for water systems, agricultural storage and more. 

To date, he explains, “In archeology we have no reliable method to detect such cavities — only chance.”  An archeologist at work may be excavating deep into the bedrock, and suddenly come across an opening that is the entrance to a hidden reservoir, but they have no way of knowing if it’s there beforehand.

This non-invasive approach offers several advantages over traditional excavation. These include preservation. As excavation is a destructive process, the ability to survey without digging protects fragile, potentially unstable sites. It is also more efficient, saving time, money and resources, enabling archeologists to precisely locate and plan their exploratory work in advance. The technology also paves the way for the discovery of hidden structures that would perhaps never have been found by chance.

According to Lipschits, subterranean structures are common in Israel because huge swathes of land contain a layer of hard limestone under which lies a softer chalk. Over millennia, inhabitants who were able to break through the upper layer were easily able to create chambers for storage, water installations, and even living spaces.

Professor Erez Etzsion of TAU’s School of Physics and Astronomy, and a member of the research team, emphasizes that one of the project’s accomplishments was demonstrating that muon detectors can be set up in an underground site with limited accessibility. To do this, researchers had to rappel into the cavern in  dark and humid conditions, using ropes and pulleys to bring in the needed scientific equipment. This is far removed from a clean laboratory with clean conditions.

Next steps for the team reported The Media Line, are smaller, cheaper and more rugged sensors, multi-detector deployments and AI-assisted reconstructions. This work will start in the Judean Foothills. As Etzion explains, a key goal will be to “create portable, affordable muon detectors and software so that excavations anywhere in the world can employ the technology.”