In this provocative book, The Cydonia Codex authors George J. Haas and William R. Saunders use archaeological research discoveries and photographs from NASA and other space programs to document the uncanny similarities between Martian and now-extinct Earth cultures. The Martian Codex begins with a review of the thirty-year history of documenting the famous “Face on Mars” landform from NASA’s first photographs in 1976 to the Mars Reconnaissance Orbiter’s HiRISE shots in 2007. Detailed analysis shows it as a split-faced structure that precisely resembles a set of masks from a temple in Cerros, Mexico. Part two provides additional examples of two-faced and composite structures all over the red planet. Haas and Saunders explore a series of recurring motifs by providing side-by-side views of the Martian geoglyphs with their terrestrial pre-Columbian counterparts. The results substantiate a commonality between two worlds in that both depict specific gods and characters from the creation mythology of the Mayan people, as recorded in the sacred Popol Vuh. This fact-based book represents the most persuasive argument yet that extraterrestrials may indeed have appeared on Earth during an earlier era.