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. In the 1980s and 1990s, biologists found that
microbial life has an amazing flexibility for surviving in
extreme environments — niches that are extraordinarily hot, or
acidic, 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 Dr. 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