Far below a mountain range in Idaho, in hydrothermal waters circulating through igneous rocks, lurks a unique community of microbes that may one day help scientists find similar forms of life on other planets. According to a report published today in the journal Nature, the newly discovered organisms are "unlike any previously described on earth."
Indeed, the researchers assert that, based on what scientists know about the subsurface chemistry of Mars, this novel ecosystem resembles what might be expected on the Red Planet. In fact, they chose the site for exactly that reason. "The water deep within these volcanic rocks has been isolated from the surface for thousands of years," explains study co-author Francis Chappelle of the U.S. Geological Survey. "It is devoid of measurable organic matter, but contains significant amounts of hydrogen."
The team discovered that this hydrogen was being put to good use. More than 90 percent of the new microorganisms belong to a primitive group known as the Archaea. But unlike Earth environments in which organisms feed on organic matter produced by plants from sunlight energy, this habitat completely lacks sunlight. "In this case," Lovley notes, "the Archaea were methane-producing microorganisms that live by combining hydrogen with carbon dioxide to make methane gas."
The finding provides the first evidence that certain microorganisms can survive without sunlight and can instead exploit hydrogen gas released from deep within the earth's surface as an energy source. "Now that such a community has been discovered, we can use it to test hypotheses about hydrogen-based subsurface life," Lovley explains, "and use these findings to develop strategies for searching for similar microbial communities on other planets."