MEXICO CITY.- A team of Mexican and U.S. scientists is preparing to peer inside one of the most iconic monuments of the ancient Maya world using a cutting-edge technique more commonly associated with particle physics than archaeology. Later this year, researchers will begin a muon-tomography study of El Castillo, the famous pyramid at Chichén Itzá, in an effort to map its interior without disturbing a single stone.

Muon tomography relies on subatomic particles known as muons, which are created when cosmic rays strike the Earth’s atmosphere and constantly rain down on the planet. Because muons can pass through solid matter, scientists can measure subtle changes in their paths to detect differences in density inside massive structures. In recent years, the technique has been used to study volcanoes and even the Great Pyramid of Giza. Now, it is being applied to the largest building by volume in Chichén Itzá.

The multidisciplinary project has been approved by Mexico’s National Institute of Anthropology and History (INAH) and brings together archaeologists, physicists, and engineers from institutions in Mexico and the United States, including UNAM, Chicago State University, and the Fermi National Accelerator Laboratory. For project leader Edmundo García Solís, the initiative represents the culmination of years of experimentation aimed at adapting high-energy physics tools to the realities of archaeological research.

El Castillo is believed to date back to the 10th century and, like many Maya temples, was built in successive layers over time. In the 1930s, archaeologists discovered an earlier structure inside the pyramid, accessed through a tunnel that led to two inner chambers: one containing a Chac Mool sculpture and another with a red jaguar throne. The first phase of the muon study will focus on these known spaces, using them as a benchmark to test the technology.

Two specially designed muon detectors will be installed inside existing tunnels on the north and south sides of the pyramid. Built to withstand cramped conditions, extreme humidity, and high temperatures, the instruments will record data over a six-month field season. If the detectors reveal unexpected anomalies, they could point to additional hidden chambers embedded within the pyramid’s core.

Researchers are careful to manage expectations. Any potential new chamber may be filled with rubble rather than empty space, making it harder to detect. Still, the promise of muon imaging lies in its ability to “see” through the entire structure, something no previous method has fully achieved.

Beyond the technical achievement, the project could help archaeologists test long-standing hypotheses, including the idea that an earlier version of El Castillo may have housed a royal burial. Whether or not new chambers are found, the study marks a significant step forward in the non-invasive exploration of one of Mesoamerica’s most celebrated monuments, blending ancient history with the tools of modern science.