<P> An extremophile (from Latin extremus meaning "extreme" and Greek philiā (φιλία) meaning "love") is an organism that thrives in physically or geochemically extreme conditions that are detrimental to most life on Earth . In contrast, organisms that live in more moderate environments may be termed mesophiles or neutrophiles . </P> <P> In the 1980s and 1990s, biologists found that microbial life has great flexibility for surviving in extreme environments--niches that are acidic or extraordinarily hot, for example--that would be completely inhospitable to complex organisms . Some scientists even concluded that life may have begun on Earth in hydrothermal vents far under the ocean's surface . According to astrophysicist Steinn Sigurdsson, "There are viable bacterial spores that have been found that are 40 million years old on Earth--and we know they're very hardened to radiation ." On 6 February 2013, scientists reported that bacteria were found living in the cold and dark in a lake buried a half - mile deep under the ice in Antarctica . On 17 March 2013, researchers reported data that suggested microbial life forms thrive in the Marianas Trench, the deepest place in Earth's oceans . Other researchers reported related studies that microbes thrive inside rocks up to 1,900 feet (580 m) below the sea floor under 8,500 feet (2,600 m) of ocean off the coast of the northwestern United States . According to one of the researchers, "You can find microbes everywhere--they're extremely adaptable to conditions, and survive wherever they are ." </P>

Organisms that are tolerant to high levels of salt high temperatures or high pressures are called