Biosphere 2 At 20

Allen Breed/ The Associated Press, 2011

Visitors tour the coastal fog desert area of the Biosphere 2 complex in Oracle, Ariz. With new projects and experiments, researchers say Biosphere 2 may be even more relevant today than when those first people passed through the airlocks on Sept. 26, 1991. The focus now is figuring out how we'll survive on our own warming planet.

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