Halfway through their two-year mission under glass, eight men and women sealed in Biosphere 2 and those watching over them are trying to prove the experiment is more than a stunt.
Their goal is to operate a space colony prototype, growing their own food and tending wildlife in a three-acre, glass-and-steel complex designed to recycle air, water and waste.Critics have said the project is unscientific because, among other things, outside air has been pumped in and a crew member who was released for medical treatment returned with supplies.
Organizers, however, hope a review by an outside panel of scientists - and some changes recommended by the experts - will give the project credibility.
Biosphere 2, on a ranch 35 miles north of Tucson, is a private, for-profit venture financed by Texas billionaire Ed Bass, who invested at least $150 million.
The experiment began with a great deal of hoopla as the four men and four women began life beyond the airlock.
But after a series of setbacks and public relations gaffes, Bass appointed an eight-member committee that includes scientists from NASA and the Smithsonian Institution to examine the project's scientific credibility.
The panel's initial report, released July 21, said Biosphere 2 had put commercial concerns - such as technology development and tourism - and public education ahead of science.
It recommended appointing a director of basic science, setting up a well-crafted science plan, pursuing scientific publication, taking steps to ensure accuracy and establishing a staff of scientists.