The owner of the hot springs, Charles Wilson, had drilled a bore hole into the hot springs to get a regular flow of hot water to heat his home and generate electricity. The researchers asked him to modify his plumbing so that they could get an uncontaminated sample of the subsurface water, and he complied.
To determine what type of microbes was most prevalent in the hydrothermal waters circulating around the deeply buried igneous rocks, the scientists analyzed DNA sequences of the organisms. The results indicated that the microbial population consisted of more than 95 percent Archaea.
Further analysis revealed that most of the microorganisms seemed to be methanogens, which make methane from hydrogen gas.
This methanogen-dominated community of microbes at Lidy Hot Springs "is unlike anything previously described on Earth," and "is consistent with geochemical scenarios proposed for microbial communities that may inhabit the subsurface of Mars and Europa," the scientists reported in their paper.
"What it shows is that the kind of ecosystem that is hypothesized to be on Europa is in fact possible," said Chapelle. "It is like Einstein making relativity predictions, but until he went out and measured deflection of stars, he didn't know he was right."
Jack Farmer, chair of the NASA Astrobiology Institute's Mars Focus Group and a professor of geology and astrobiology at Arizona State University in Phoenix, supports the connection that Chapelle, Lovley, and their colleagues make between the microbial community in Idaho and possible life on Mars and Europa.
"Because there is evidence that Mars once hadand probably still does havea widespread subsurface groundwater system, and, in the past, at least, widespread volcanic activity that could drive hydrothermal systems, hydrogen-eating microbes could have developed and persist there deep beneath the surface," said Farmer.
Evidence, as yet unproven, also suggests Europa may have microbial life, Farmer said. Europa has a subsurface ocean and hydrothermal heating as a result of a gravitational tug-of-war between Jupiter and other large moons.
Are Archaea out there?
In search of an answer, NASA has a Mars-exploration program. It will culminate in 2007 with the launch of a robotic probe that will dig near the surface of the planet in search of life, past or present, said Farmer.
"What we would really like to do to answer this question is deep-drill to depths of hundreds to thousands of meters," said Farmer. "The technology for intermediate and deep drilling from a robotic platform does not yet exist, although there are active efforts within the community and NASA to develop these capabilities," he noted.
Although Farmer, Chapelle, and their colleagues say they have no scientific basis to prove the existence of life on other planets, findings like those at Lidy Hot Springs give them the gut feeling that extraterrestrial life will one day be found.
Chapelle said: "I think it is inconceivable that there is not this kind of metabolism in other places."
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