In an underground chamber in Guatemala, archaeologists have discovered the earliest evidence so far of Mayan astronomical tables: dates, numbers and depictions of lunar deities painted or carved on the walls some 1,200 years ago.

William Saturno at Boston University in Massachusetts and his colleagues stumbled across the paintings (pictured) while excavating the Mayan city of Xultun. On one wall the researchers found a table containing four columns of numbers, which could represent recurring events related to the cycles of Venus, the Moon, Mars and possibly Mercury. A table on another wall seemed to show 27 columns of dates, each 177 or 178 days apart, with Moon deities at the top of each column. The Maya recorded movements of the Moon in semesters of 177 and 178 days, or six lunar months.

Credit: T. TURNER/NATIONAL GEOGRAPHIC

Science 336, 714–717 (2012) 10.1126/science.1221444