Scientists have turned to subatomic particles known as muons to scan the 4,500-year-old pharaonic mausoleum.
By Rossella Lorenzi
For the past 23 years researchers have been trying to unlock the mysteries of the Great Pyramid in Giza using tomb-raiding robots. Now scientists have turned to subatomic particles known as muons to scan the 4,500-year-old pharaonic mausoleum. The aim is to detect voids that might point to hidden chambers and tunnels.
The full scan of the iconic monument is one of several ambitious steps of ScanPyramids, a project carried out by a team from Cairo University's Faculty of Engineering and the Paris-based non-profit organization Heritage, Innovation and Preservation (Hip Institute) under the authority of the Egyptian Ministry of Antiquities.
In April the team was able to reveal for the first time the internal structure of the Bent pyramid at Dahshur, using cosmic particles.
In a statement released on Tuesday, the ScanPyramids team detailed three non-invasive techniques employed at Giza. The results of the survey will be shared with several committees representing different scientific disciplines. One of them will gather a number of Egyptologists led by the former minister of Antiquities Zahi Hawass.
"Our team is trying to get evidence from the field that some voids exists. Then it will be the role of historians, Egyptologists, architects, to tell why those voids are there," Mehdi Tayoubi, co-director of the ScanPyramids mission, told Discovery News.
Built for the pharaoh Cheops, also known as Khufu, the Great Pyramid is the last remaining wonder of the ancient world.
The monument is the largest of a family of three pyramids on the Giza plateau, on the outskirts of Cairo, and has long been rumored to have hidden passageways leading to secret chambers.
Archaeologists have long puzzled over the purpose of four narrow shafts deep inside the pyramid since they were first discovered in 1872.
Two shafts extend from the upper or "King's Chamber" exit into open air. But the lower two, one on the south side and one on the north side in the so-called "Queen's Chamber" disappear within the structures, deepening the pyramid mystery.
Widely believed to be ritual passageways for the dead pharaoh's soul to reach the afterlife, these 8-inch-square shafts remained unexplored until 1993, when German engineer Rudolf Gantenbrink sent a robot through the southern shaft.
After a steady climb from the heart of the pyramid, the robot came to a stop in front of a mysterious limestone slab adorned with two copper pins.
In 2002, Hawass explored the southern shaft on live television. As the world held its breath, a robot pushed a camera through a hole drilled in the copper pinned door — only to reveal what appeared to be another door.
The following day, Hawass sent the robot through the northern shaft.
After crawling for 213 feet and navigating several sharp bends, the robot came to an abrupt halt in front of another limestone slab.
As with the Gantenbrink door, the stone was adorned with two copper pins.
In the attempt to finally solve the mystery, Hawass established in 2011 the Djedi project, a joint international-Egyptian mission (Leeds University, Dassault Systèmes). The project began with the exploration of the southern shaft, which ends at the so called "Gantenbrink's door."
The robot was able to climb inside the walls of the shaft while carrying a bendy camera, small enough to fit through a small hole in a stone door at the end of the tunnel.
This gave researchers a clear view into the chamber beyond. It was at that time that the micro snake camera sent back images of 4,500-year-old markings believed to be engineering numbers.
The project was then halted following the Egypt revolution.
"I dedicated my whole life to study the secrets of the Great Pyramid. My goal is to finally find out what's behind these secret doors," Zahi Hawass told Discovery News in a past interview.
He will now have another chance with the ScanPyramids's innovative and non destructive technologies.
Tayoubi explained to Discovery News that the first of the three employed techniques relies on muons. These cosmic particles permanently and naturally rain on Earth and are able to penetrate any material very deeply.
Overall, 80 emulsion films made by Nagoya University, Japan, have been placed inside the Great Pyramid at different places, in the Queen's chamber, Queen'schamber niche, and lower chamber.
"They will be exposed to the muons' natural flow for 40 days," Tayoubi said.
The films will then be analyzed to generate muon radiographies images, potentially revealing hidden chambers in the pyramid.
"In case a void is detected, the images generated from the emulsion film analysis show a contrast difference," Tayoubi said.
"It is a very accurate but very long process," he added.
The second technique uses gas electronic detectors specially fabricated by the CEA (French Alternative Energies and Atomic Energy Commission). These were placed outside the Great Pyramid.
Tayoubi explained that each time a muon gets through a gas detector it generates an electrical signal that is captured in real time.
"With two detectors we are then able to calculate the muon trajectory and to count them. We can then generate in real time a muography image that becomes more accurate the more we let the telescopes exposed," Tayoubi said.
The detectors will be running for a whole month of calibration in order to detect known voids. Then they will be pointed to specific targets trying to identify unknown voids. A third detector will be used in the next days.
The last technology is based on a plastic electronic scintillator conceived and made by the High Energy Accelerator Research Organization (KEK – Japan). Made of a grid with a special plastic which is sensible to muons, the scintillator basically works like the gas detectors although it is less accurate.
"It will be placed inside the Queen's chamber in July," Tayoubi said.
He added that preliminary results are not expected before September-October.