University of Arizona Biosphere 2 is an American Earth system science research facility located in Oracle, Arizona. Its mission is to serve as a center for research, outreach, teaching, and lifelong learning about Earth, its living systems, and its place in the universe. It is a 3.14-acre (1.27-hectare) structure originally built to be an artificial, materially closed ecological system, or vivarium. It remains the largest closed ecological system ever created. Constructed between 1987 and 1991, Biosphere 2 was planned to experiment with the viability of closed ecological systems to support and maintain human life in outer space as a substitute for Earth's biosphere.