When Donald Slater received his first freshly published, yellow-bordered copy of National Geographic from his grandfather, he never thought that he would one day see his own work published in the magazine. Now a museum educator at Andover’s Peabody Museum of Archaeology, Slater will be featured as a National Geographic Explorer in a forthcoming edition for his discovery of lost ancient Mayan caves in southeastern Mexico. Slater said, “National Geographic is one of the things that got me into archaeology as a kid, and so it was definitely exciting to hear that I was going to be featured in it.” Slater began his expedition in 2009 after receiving a $14,000 grant from the National Geographic Society and the Waitt Institute for Discovery. According to Slater, the grant enabled him to assemble a group of experienced archaeologists, cavers and locals who helped him during the expedition. The fieldwork he conducted during the expedition formed the foundation for his dissertation. His dissertation, known as the Central Yucatan Archaeological Cave Project, focused on his discovery of cave images and ancient artifacts that relate to Mayan spiritual beliefs and rituals. “To the ancient Maya, the earth was believed to be an animate being, often times depicted as a giant turtle or a giant crocodile, and the interior of the earth was thought to be a realm where gods, spirits and ancestors lived,” said Slater. “To them, caves were portals to the spiritual realm where people could access ancestors and deities,” he continued. Slater and his crew have excavated in four caves, located and took GPS points for over 100 more caves and produced detailed maps for about 10 caves over the course of six trips to the Yucatan Peninsula. In addition to finding the caves, Slater and his team have found petroglyphs, rock carvings, over 40,000 broken pieces of ceramics, different ornaments made out of imported shell and jade, pathways and staircases carved into the cave, as well as blades that might have been used for sacrificial rituals. Among many discoveries, Slater said the most interesting one was an astronomical observatory inside the cave, a platform that aligned with a pyramid outside the cave. When the sun reaches its solar zenith, its light is directed on the top of the pyramid and can be seen from the cave. “[The solar zenith] only happens twice [a year] in the tropics, and it’s the day when the sun is directly overhead. The first time that it happens in this area where I’m working in Yucatan is right around the time of the first rain, so it [was] a really important part of the Mayan solar agricultural calendar,” Slater further explained. Slater said that his favorite moment of the expedition was participating in the modern Mayan rain-making ceremony, called Cha Chaak, after earning the trust of the locals who aided him in his expedition. “We became very friendly with the locals, built some good relationships and were able to convince [the locals] that the work we were doing was legitimate and that we wanted a formal partnership, and not just to take advantage of people. We finally got permission, and after all that work, it was really rewarding,” explained Slater. Despite these moments of triumph, Slater encountered many obstacles in his expedition. His camp almost burned down twice because of the slash-and-burn agricultural technique practiced in neighboring Yucatan villages. His crew also suffered from intestinal worms that spread through the camp. “I think for me, the biggest challenge was being away from my family for four months at one time. I hadn’t done one that long before, and I don’t plan to do one that long again, at least for a long time. Being away from my family was very difficult,” added Slater. Slater is currently working on his dissertation paper, which he hopes to finish by next year.