MEXICO CITY, MEXICO—Hundreds of small spheres have been spotted by the Tlaloc II-TC robot in the newly discovered chambers beneath the Temple of the Feathered Serpent at Teotihuacán. The spheres have a core made of clay and are covered with a material known as jarosite, which is formed by the oxidation of pyrite. “Pyrite was certainly used by the Teotihuacanos and other ancient Mesoamerican societies. Originally the spheres would have shown brilliantly. They are indeed unique, but I have no idea what they mean,” commented George Cowgill, professor emeritus at Arizona State University. Scholars think they may find the remains of the city’s rulers in these chambers.