8 men and women once sealed themselves inside this enormous fake Mars colony for 2 years. Here's what it's like today.

· Biosphere 2 was a highly ambitious experiment to simulate a self-sustaining Mars colony in the Arizona desert.
· The 3.14-acre, bubble-like facility cost $250 million to build and operate.
· Eight men and women locked themselves inside for 2 years and experienced one incredible challenge after another.
· Though the...