Sixteen months into a two-year experiment, eight people sealed inside a glass building in the Arizona desert were slowly running out of oxygen, and nobody could figure out where it was going. Biosphere 2 sits near Oracle, north of Tucson. Built with roughly $150 million from billionaire Ed Bass, the massive glass complex contained a rainforest, ocean, mangrove wetland, savannah, desert, agricultural area and living quarters. On September 26, 1991, eight people entered and the doors were sealed behind them for two years. They had to grow their own food, recycle their water and maintain their own atmosphere. Then the oxygen started disappearing. It began around 20.9%, but over 16 months fell to roughly 14.5%, similar to breathing at about 13,000 feet. Crew members became exhausted, struggled climbing stairs and sometimes had to stop mid-sentence to catch their breath. The oxygen wasn’t simply leaking out. Microorganisms in the soil were consuming oxygen and releasing carbon dioxide...