Scientists have found a place on Earth that they believe is the same as conditions on Mars and on Jupiter?s moon Europa. Since the site is teeming with a large number of microbes, they believe that Mars and Europa could be too.
The site is Lidy Hot Springs, located in the Beaverhead Mountains in Idaho. Living in hydrothermal waters 660 feet below the surface are microscopic organisms called methanogens, which get their energy from hydrogen and produce methane as a byproduct. Scientists agree that if extraterrestrial life does exist elsewhere in the solar system, it?s probably in the form of organisms at the bottom of the food chain, which have a simple metabolism and need only hydrogen and carbon dioxide to survive.
?Those two things are very common in the universe,? says Francis Chapelle of the U.S. Geological Survey in Columbia, South Carolina. ?It is a kind of metabolism that can happen independent of photosynthesis.? In other words, this type of life can exist in places where green plants can?t survive.
Methanogens are a part of Archaea, which were first discovered in the 1970s. Archaea inhabit environments with harsh conditions, such as hydrothermal vents at the bottom of the ocean, petroleum deposits, and the digestive tracts of cows.
Archaea are genetically different from similar bacteria. Bacteria, which dominate our ecosystem, live where there is organic matter and photosynthesis. Archaea can live in environments lacking organic carbon.
Scientists had already theorized that methanogens could exist on Earth and on other planets and moons. But no place dominated by the them had ever been found on Earth until they were discovered in Lidy Hot Springs.
?There [was] this idea that there might be these communities,? says Derek Lovley, a microbiologist at the University of Massachusetts. ?People have looked for a while, but the problem is that almost everywhere there is a significant amount of organic matter.?
In order to find an environment in which Archaea dominated, the researchers searched for a place lacking organic carbon. They focused on the hot springs in eastern Idaho because volcanic activity had burned away most of the organic carbon that could serve as an energy source for microorganisms but the water contained high concentrations of geologically produced hydrogen.
?Lidy Hot Springs does not have organic matter,? says Lovley. ?The only thing there is hydrogen percolating up.?
Charles Wilson, the owner of the hot springs, drilled a bore hole into them 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.
To determine what type of microbes was most common in the hydrothermal waters circulating around the deeply buried rocks, the scientists analyzed the 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 are methanogens, which make methane from hydrogen gas.
This methanogen-dominated community 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 Europe,? according to the scientists who are studying the area.
?What it shows is that the kind of ecosystem that is hypothesized to be on Europa is in fact possible,? says 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, says,?Because there is evidence that Mars once had?and probably still does have?a 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.?
Evidence also suggests Europa may have microbial life, Farmer says. Europa has a subsurface ocean and hydrothermal heating as a result of a gravitational tug-of-war between Jupiter and other large moons.
If it survives the latest budget cuts, the NASA Mars-exploration program 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. ?What we would really like to do to answer this question is deep-drill to depths of hundreds to thousands of meters,? says 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.?
Findings like those at Lidy Hot Springs give scientist the hope that extraterrestrial life will one day be found. Chapelle says, ?I think it is inconceivable that there is not this kind of metabolism in other places.?
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Scientists have now discovered that E coli of stomach bug fame is capable of amazing feats of survival, withstanding up to 16,000 times the pressure it normally faces at sea level.
?The take home lesson is that we should be looking beneath the surface of planets: under the polar caps of Mars or beneath the surface of the Jovian moons,? says James Scott of the Carnegie Institution in Washington.
He and his colleague Anurag Sharma found that even at the kind of pressures that exist 31 miles below the surface of the Earth, E. coli can survive. ?We can?t say that they?re thriving but we can see that they are surviving. They?re moving around and they?re metabolizing,? Scott says. ?What all this says to us is that pressure is not going to be a key detriment to finding life.?
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