Nuclear physicists have claimed to have identified one of the oldest-known churches in the word using using cutting-edge scanning techniques.
The mysterious structure had been mostly buried underground, and is located within the confines of a medieval fortress in the Russian city of Derbent.
Experts had argued that the construction was a water tank, a church, or a fire temple — but the fortress’ protected status prevented archaeological digs to investigate.
To get around this, researchers are using special detectors to study how subatomic particles called muons, created by cosmic rays, travel through the building.
This muon scanning technique allows researchers to reconstruct a 3D image of the subterranean building’s exterior without needing to do any digging.
Although the researchers are planning a more detailed scan, the have already shown that the outside of the building was cross-shaped and orientated north-south.
These architectural features are consistent with the notion that the building was indeed a church — which would make it the earliest-known example in Russia.
The mysterious half-buried structure, long argued to be a water tank, is located within the walls of the medieval fortress of Naryn-Kala, in the city of Derbent in the Russian Republic of Dagestan and dates back to around 300 AD.
The building is almost completely buried underground, with only a fragment of its half-destroyed, wire-frame dome visible above ground.
Physicists led by Natalia Polukhina of the Russian Academy of Sciences tested a scanning technique called muon tomography — which is similar in principle to the CT scans used in hospitals — on the structure between May and September 2018.
The team placed several muon detectors in the mostly-buried building at depths of around 33 feet (10 metres) from the surface of the fortress’ interior — with each containing ’nuclear emulsion’, the muon equivalent of a photographic plate.
From the images collected by the emulsion, the researchers have been able to create a three-dimensional reconstruction of what the outside of the structure would have looked like before it was buried.
The cross-shaped building extends 49 ft (15 metres) from north to south and 44 ft (13 m) from west to east. Each arm of the cross is around 16 ft (5 m) wide and three are 14 ft (4 metres) long whereas the fourth is over 20 ft (6 metres) in length.
Between the building’s cruciform shape and vaulted rooves, the researchers propose the structure is likely a church, which would make the buried structure not only the most ancient church in Russia but one of the oldest known from across the world.
Researchers turned to muon tomography to study the mostly-buried structure because a conventional archaeological dig would be impossible at the site given the risk of damaging the surrounding fortress, which is a UNESCO cultural heritage site.
Experts believe the building, located in the northwestern part of the fortress, was covered over with soil by Arabs who captured Derbent in around the year 700 AD.
The original purpose of the structure has been a subject of debate, however, with some historical and reference texts referring to the construction as being built to serve as an underground water tank.
During the 17—18th centuries the structure had been pressed into such a use, but the researchers are sceptical that the building was designed for this purpose.
’It seems very strange to me to interpret this building as a water tank,’ Dr Polukhina said in a statement.
’In the same fortress of Naryn-Kala, there is an equal underground structure of 10 meters depth, and it really is a tank; this is just a rectangular building.’
’The unusual building, in which we have put our detectors, has the shape of a cross, oriented strictly to the sides of the world, one side is two meters longer than the others.’
This configuration would seem more in line with other sources that propose the building was either a church or a fire temple — a Zoroastrian place of worship.
’As the archaeologists who began excavations say, during construction, the building was entirely on the surface and it stands on the highest point of the Naryn-Kala,’ added Dr Polukhina.
’What is the sense to put the tank on the surface, and even on the highest mountain? It is strange. Currently, there are more questions than answers.’
The buried structure at Naryn-Kala is not the first ancient building to be scanned using muon tomography.
In 2017, researchers revealed the discovery of huge and previously unknown chamber — dubbed ’the big void’ — located within the Great Pyramid of Giza in Egypt.
’Although there is currently no information about the intended purpose of this void, these findings show how modern particle physics can shed new light on the world’s archaeological heritage,’ the team had concluded in their Nature paper.
Alongside forming a rough image of the structure of the church, the team also recorded an anomaly in the distribution of muons passing through the western wing of the building, which they believe may be an architectural feature of some kind.
Although the results of the study are revealing, the research was only intended as a preliminary step — one to determine the best optical exposure and the optimum configuration of detectors for scanning this particular building.
The reliability of using muon tomography at Naryn-Kala had not been certain before the test, with the shelly limestone walls and the density similarity between the buried structure and the surrounding church having the potential to present difficulties.
With this initial step a resounding success, however, the researchers are now planning a full-scale scan of the building which will allow them to determine the full contours of the buried structure.
To improve the final scan of the structure, the researchers will install additional detectors on the western slope of the fortress.
The full findings of the study were published in the journal Applied Sciences.