ORACLE, Ariz. -- Jane Poynter and seven compatriots agreed to spend two years sealed inside a 3-acre terrarium in the Sonoran Desert. Their mission back in the 1990s: To see whether humans might someday be able to create self-sustaining colonies in outer space.

Two decades later, the only creatures inhabiting Biosphere 2 are cockroaches, nematodes, snails, crazy ants and assorted fish. Scientists are still using the 7.2-million-square-foot facility, only now the focus is figuring out how we'll survive on our own warming planet.

Next month, workers will begin a new chapter for "B2" -- building the first of three enclosed soil slopes in what was once the "intensive agricultural biome," the space where Poynter and the other original "biospherians" grew the rice, sorghum, peanuts, bananas, papayas, sweet potatoes and lablab beans that supplied 90 percent of their nutritional needs.

The new "Land Evolution Observatory," a 10-year, $5-million project, will help scientists learn how vegetation, topography and other factors affect rainwater's journey through a watershed and into drinking supplies.

"What makes me really happy is that it really does capture a lot of what we were trying to do in the early years of Biosphere 2," says Poynter, who founded an aerospace company with husband and fellow biospherian Taber MacCallum. "I mean, they're doing some world-class science. They really have the vision of the place. They understand what it was intended for in many ways."

And researchers say Biosphere 2 may be even more relevant today than when those first people passed through the airlocks on Sept. 26, 1991.

Located about 30 miles northeast of Tucson in the foothills of the Santa Catalina Mountains, B2 rises out of the high-desert landscape like a giant glass-and-steel ziggurat.

In a story previewing that first mission in 1991, The New York Times described Biosphere 2 (Earth is "Biosphere 1") as a "combination greenhouse and futuristic shopping mall."

But with its network of interconnected domed chambers and observatory-topped tower, anchored by the 91-foot-high pyramid and its 6,500 double-laminated windows, the complex resembles nothing so much as one of those plastic Habitrails for hamsters and gerbils. Which is apt, since Poynter and the other biospherians -- four men and four women -- were very much human guinea pigs.

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