(singular: archaeon) a group of tiny organisms often living in extreme environments, such as ocean vents and salt lakes. (nationalgeographic.org)
AB: Since many astrobiologists are currently examining hydrothermal vents, in search of extremophiles, does the prebiotic chemistry actually get decomposed rather than enhanced by the presence of such ocean venting? (astrobio.net)
A marine biologist describes her upcoming mission to some of the deepest hydrothermal vents in the ocean (scientificamerican.com)