A decade before Elon Musk founded his fast-rising rocket company, SpaceX, or ever spoke publicly about colonizing Mars, a different billionaire captivated the world with Biosphere 2.
Oil tycoon Ed Bass spent about $250 million to build and operate that facility as a proof-of-concept for a permanent, self-sustaining habitat on Mars. Four men and four women sealed themselves inside the nearly airtight space in September 1991 and emerged two years later.
The experimental space-age facility served as the stage for a spectacular and controversial story of human endurance. Built into a hillside of the Arizona desert during the early 1990s, the complex remains a functional marvel of engineering.
Business Insider recently visited Biosphere 2 to learn about the many challenges that early Martian colonists could face.
Here’s what it’s like inside the 3.14-acre bubble today.
Biosphere 2 is nestled in the foothills of the Santa Catalina Mountains in Oracle, Arizona. The area is part of the Sonoran Desert: an arid, unforgiving, and eerily Mars-like region that stretches from western Mexico into the US Southwest. 
Sources: Biosphere 2, Business Insider
A roughly 80-foot-tall glass pyramid poking out of the hillside greets visitors. 
Sources: Biogeosciences, Business Insider
Farther west are other futuristic structures on the sprawling 40-acre campus. 
Sources: “The Human Experiment: Two Years and Twenty Minutes Inside Biosphere 2“, Business Insider
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