"Extremophiles" are strange organisms that can live in shocking extremes of cold, heat, pressure, acidity and more. Researchers discovered creatures that dwell in solid rock two miles deep in the Earth and survive by "eating" the breakdown products of radioactivity. Research on these organisms is redefining the limits of life on Earth and forcing scientists to reconsider the probability of life on other worlds.
You can learn more about these extreme microbes in the National Science Foundation online Special Report, X-treme Microbes.
Credit: Nicolle Rager Fuller, National Science Foundation