Once upon a time, scientists routinely found life in places where it wasn't supposed to exist. That doesn't happen anymore, and not because the pace of discovery has slowed. If anything, it's accelerated. It's simply become clear that life can exist almost anywhere on Earth.
After 3 billion years of evolution, life has flowed into every last nook and cranny, from the bottom of the sea to the upper edge of the stratosphere. From blazing heat and freezing cold to pure acidity and atomic bomb-caliber radiation, there's seemingly no stress so great that some bug can't handle it.
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Desulforudis audaxviator is perhaps the one truly singular microbe. Every other known organism exists in a system in which at least some nutrients are provided by other creatures. But not D. audaxviator, which was discovered in a South African mine shaft, two miles beneath Earth's surface and entirely alone. Using radioactivity from uranium-containing rocks as energy, it can harvest or metabolize every nutrient it needs from surrounding rock and gas — the world's only known single-species ecosystem.
