It's pitch black, toxic gases bubble up from deep below, sulfuric acid drips from above, and carbon monoxide fills the air. It is the interior of a startlingly beautiful, and treacherous, cave. Scientists are penetrating the depths of incredible caverns like this one, discovering abundant life hidden in the dark, and shedding new light on how life may have begun on earth and may exist on Mars and other worlds. Explore Cueva de Villa Luz in Mexico, an active and dangerous cavern that teems with life despite the dark and noxious environment. Travel to Carlsbad Caverns and learn how this tourist attraction concealed an astonishing scientific secret. Squeeze through the deepest cave in New Mexico's Lechuguilla, home to the world's most stunning and fragile cave formations.