** ADVANCE FOR USE TUESDAY, APRIL 26, 2011 AND THEREAFTER ** FILE - In this Sept. 26, 1993 file picture, Abigail Alling stands on the balcony of the living quarters inside Biosphere 2 above the agricultural growing area of the complex in Oracle, Ariz. Eight people agreed to spend two years sealed inside the 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. But 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. (AP Photo/Jeff Robbins)