: With the use of muon detectors, researchers in Mexico have discovered that Teotihuacan’s enormous Pyramid of the Sun is deteriorating. Arturo Menchaca of the National Autonomous University of Mexico and colleagues tracked the paths of muons
through the structure to look for internal chambers. Although they found none, they did notice that one side of the pyramid is significantly drier than the other. While the moisture difference poses no immediate danger, archaeologists are now working to determine the best method of maintaining the structure.