From Wired Magazine:
How can we look for weird tentacled things living unimaginable lives under indescribable skies if we're still mostly stuck on Earth? I believe that the best place to find life on Mars will be underground, not the cold, radiation-blasted deserts of the surface. So I look to a model system on our planet: caves. The Martian subsurface might have water, or it might have ecosystems as weird as the poisonous, sulfuric acid-soaked Cueva de Villa Luz in the Mexican state of Tabasco. For six years, I've studied the chemistry and strange denizens of Villa Luz. But working there can be hazardous - even life-threatening.