Biosphere 2: Eight People, Two Years, One Sealed World

On September twenty-sixth, nineteen ninety-one, eight people walked into a three-acre glass and steel structure in the desert north of Tucson and sealed the doors behind them. They would not leave for two years.

The facility was called Biosphere Two, the name reflecting the premise that Earth itself is Biosphere One. Built between nineteen eighty-seven and nineteen ninety-one by the company Space Biospheres Ventures, it was designed to be the largest fully closed ecological system ever constructed, a test of whether humans could build a self-sustaining artificial world capable of supporting human life in space. Inside its glass enclosures: a tropical rainforest, an ocean with a coral reef, a savanna, a fog desert, a mangrove wetland, and an agricultural zone.

The eight crew members, called biospherians, included physician Roy Walford, Jane Poynter, Taber MacCallum, Mark Nelson, Sally Silverstone, Abigail Alling, Mark Van Thillo, and Linda Leigh. They were to grow eighty-three percent of their own food, maintain all the ecosystems, and conduct scientific research. The first problem appeared within months.

The oxygen level inside began dropping. Over sixteen months, it fell from the atmospheric normal of roughly twenty-one percent to fourteen and a half percent, the equivalent of living at an altitude of thirteen thousand feet. Some biospherians developed symptoms. The agricultural system produced enough calories to keep the crew alive but not enough to prevent constant hunger during the first year. The concrete in the structure, still curing, was absorbing oxygen from the air.

Oxygen was eventually injected from outside, a compromise that drew criticism. The mission ran its full two years, ending September twenty-sixth, nineteen ninety-three. The University of Arizona now operates the facility as a climate research center. The glass structure in the Oracle desert remains the largest closed ecological system ever built by human hands.