Chichén Itzá, Yucatan — The INAH says they are preparing a mapping exercise to detect interior structures in El Castillo at Chichén Itzá. Both Mexican and American scientists will install two muon detectors in the tunnels of the pre-Hispanic pyramid.
The investigation, they say, is aimed at identifying the Offering and Sacrifice rooms and possibly another hidden chamber.
A team of Mexican and American scientists are finalizing preparations to perform a CT scan of Chichén Itzá ‘s main building El Castillo. By detecting muons, subatomic particles produced by cosmic rays, they will investigate the interior of this pyramid which measures nearly 55.5 meters on each side.
According to the National Institute of Anthropology and History (INAH), the 30 meters tall pyramid is the largest by volume in the ancient Mayan city.
The multidisciplinary initiative, endorsed by the Archaeology Council of theINAH, links the knowledge and efforts of specialists from this institution and physicists and engineers from various departments of the National Autonomous University of Mexico (UNAM), Chicago State University, Dominican University and Virginia University, as well as the Fermi National Laboratory, America’s particle physics and accelerator laboratory.
The project’s lead researcher, Edmundo García Solís, says during the last quarter of 2025, years of experimentation will come to fruition to test the effectiveness of muonic imaging on one of the most important pre-Columbian monuments on our continent, with detection equipment designed and built by North American scientists.
The director of the Chichen Itza Archaeological Zone, Guadalupe Espinosa Rodriguez, explained that the Castle is believed to date back to the 10th century, and like other Mayan temples, it is the product of the superposition of several construction phases.
In the 1930s, archaeologists Eduardo Martínez Cantón and José Erosa Peniche excavated a tunnel from the western balustrade of the north side, which led them to the so-called Offering and Sacrifice Halls.
In the former, they found a Chac Mool sculpture, and in the latter, a red-painted jaguar throne. Now, using two tunnels that provide access to this interior structure, the first test with the new technology will be the exploration of both halls.
García Solís, whose research area at Chicago State University is experimental high-energy nuclear physics, acknowledges the previous work of the team from the Institute of Geophysics and the Faculty of Engineering of UNAM, which, in 2016, implemented an electrical resistivity tomography, based on flat electrodes to explore the interior, through which there are indications of a space within the substructure, located in the 1930s.
However, it highlights the unlimited depths that large-volume imaging using muons can reach, which would allow obtaining a tomography of the entire surface of the pyramid.
In Teotihuacan, the existence of a tunnel located eight meters below the Pyramid of the Sun, and which reaches close to the center of the base, represented an extraordinary opportunity to carry out a similar experiment, by a group led by the researcher Arturo Menchaca Rocha, from the Institute of Physics of the UNAM, a member of the team that will now enter El Castillo.
To this end, as García Solís explained, two identical muon detectors were built and will be installed in the north and south tunnels of the pyramid. Their electronic components consist of three foldable panels (60 cm by 1 m) mounted on a structure, giving each detector a dimensions of 1.40 meters by 68 cm and a height of 1.50 meters,
For its design, “we worked in reverse to how we are used to in experimental physics, adjusting to an existing space, reduced in dimensions, and where a humidity of almost 100 percent prevails, which means that the air is completely saturated with vapor, and around 32 degrees Celsius.
“These detectors measure the difference in density. The extreme of the density difference is a void. If we want to confirm the existence of a third chamber, it is likely that it will be filled in, as the archaeologists indicate.
“Therefore, it will take longer to locate it, since the amount of data needed to locate a chamber is inversely proportional to the density difference between the chamber and the rest of the pyramid.”
“During this six-month field season, we expect to distinguish the known chambers with reasonable certainty. Once we achieve this, we will evaluate the dataset, hoping to observe anomalies that indicate a third chamber; if so, we will reposition both detectors to determine their dimensions. That would be the extent of our contribution,” García Solís explained.
Thus, this prospective technique could help to rule out or support hypotheses put forward by archaeologists, such as Virginia E. Miller, a retired professor from the University of Illinois and a specialist in Yucatan architecture, who has postulated that an earlier substructure in El Castillo could have been the site of a royal burial.
