Life Forms >> Extremophiles
Life abounds in the most unexpected placeseven extreme places. An organism that thrives in an extreme environment is called an extremophile. In the past decade, the search for this type of life has exploded. Discoveries about microscopic life inside seafloor vents are just one example. As we learn more about these organisms, we may learn more about the possibility of life beyond Earth.
Credit: Nicolle Rager Fuller, NSF
Life exists not just around vents, but inside them too. Unlike the life forms that crawl or swim around the vents, those inside are invisible. These microscopic bacteria (one-celled organisms) not only survive but even thrive in the dark and hot environment of the vent. In the absence of sunlight, specially adapted bacteria and similar organisms called Archaea convert the vent chemicals to usable bioenergy, in a process analogous to plants’ ability to use sunlight.
Researchers have discovered a bizarre group of microbes that live inside rocks in the inhospitable geothermal environment at Wyoming’s Yellowstone National Park. One scientist describes the life–form, found in the pores of rocks in a highly acidic environment, as “pretty weird,” and resembling a lichen. Scientists believe similar kinds of geothermal environments may have once existed on Mars. The Yellowstone discovery may help steer the hunt for evidence of life on Mars.
Antarctica Subglacial Lakes
In addition to the super-hot environment of sea vents and hot springs, bacterial life may also exist in the cold, dark environment beneath the Antarctic ice sheet. Scientists aren’t yet sure, but the suggestions are strong. Two separate research teams have drilled into Lake Vostok, a suspected body of water below the Antarctic ice sheet. (It is still “suspected,” and not proven, because scientists are reluctant to explore further until they know their actions will not contaminate a potentially unique environment.) Both teams found bacteria inside ice that is believed to be created from lake water. DNA analysis indicates that although the bacteria have been isolated for millions of years, they are biologically similar to known organisms.
Scientists now know that life exists not only in very hot and very cold liquid environments, but in a very dry environment as well. Environmental microbiologists have discovered evidence of microbial life about a foot below the rough terrain of Chile’s Atacama desert, one of the driest places on Earth. Their finding contradicts previous beliefs that the desert is too dry to support life, and may influence how scientists look for life in the similarly dry environment of Mars.
Some scientists speculate that if life does exist beyond Earth, it might be the form of vent bacteria. Because these microscopic life forms have already proven their ability to survive in the extreme environment of Earth’s hydrothermal vents, they might also survive in similar environments elsewhere – for example, on Europa. Europa is one of Jupiter’s moons, and is covered in ice. Scientists have recently uncovered strong evidence of liquid water beneath Europa’s ice, which may be due to hydrothermal vents, which may in turn host bacteria. Alternatively, scientists who have found evidence of bacteria living inside Antarctic ice speculate that they may also live inside Europa’s ice. The questions exceed the answers, but the clues are tantalizing.