The US National Imagery and Mapping Agency has released images taken of Antarctica's McMurdo Dry Valleys region from spy satellites in 1975 and 1980. Researchers at the US Antarctic Program, an office of the National Science Foundation, will use the photo-reconnaissance data to study the ecological dynamics of the 4800-km2 polar desert site, which is the largest predominantly ice-free region on the continent. The images include a wide-angle photo taken in 1975 that establishes a baseline against which the current conditions can be compared, according to project manager Scott Borg. Researchers will analyze hydrologic change, which affects the presence and stability of life in the area, as well as glaciological and geological developments. The McMurdo Dry Valleys region is the only polar desert in a 21-site, long-term ecological study by the National Science Foundation that includes temperate, marine and urban systems in the Western Hemisphere. The harsh ecosystem is home largely to microorganisms, mosses and lichens.