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Earth Microbes Support Martian Life Hypothesis: Study

Posted on: Tuesday, 6 December 2005, 09:00 CST

Earth microbes support Martian life hypothesis: study

LOS ANGELES, Dec. 5 (Xinhua) -- Methane-producing microbes are eking out an existence 3 km below the surface of Greenland, scientists said on Monday, providing support for the hypothesis that methane in Mars' atmosphere could be produced by life.

The research group led by Buford Price, professor of the University of California at Berkeley, reported these findings in the Proceedings of National Academy of Sciences.

The microbes, called methanogenic archaea, produce methane as a byproduct of their metabolism. They are known to be capable of living under extremely rigorous conditions.

Examining the ice cores for methane concentrations and the presence of methanogens, the researchers found that unusually high amounts of methane found near ice core bottoms appear to be produced by methanogens detected at the same depths.

Most of these microbes have been living for more than 100,000 years, and the researchers hypothesized that they barely survive, repairing cellular damage but unable to expand their populations.

"The metabolic rate we estimated for microbes at those depths is consistent with microbes imprisoned in rock, sediment, and ice, " the researchers wrote in the paper.

"It is roughly the same as the rate of spontaneous macromolecular damage inferred from laboratory data, suggesting that microbes imprisoned in ice expend metabolic energy mainly to repair damage to DNA and amino acids rather than to grow."

Scientists have suggested that the presence of methanogens on Mars is one way to explain the planet's surprisingly high atmospheric methane concentrations, since sunlight should quickly destroy the methane on the red planet, and a purely chemical mechanism to sustain the observed levels seems unlikely.

The team calculated that one methanogen per cubic centimeter, spread across the Mars 10 meters thick at a depth where the temperature is near the freezing point of water, could account for the observed Martian methane levels.

"Equating the loss rate of methane recently discovered in the Martian atmosphere to the production rate by possible methanogens, we estimate that a possible Martian habitat would be at a temperature of 0 degree Celsius and that the concentration, if uniformly distributed in a 10-m-thick layer, would be 1 cell per ml," they said.

The researchers said they are constructing a bore-hole fluorimeter to detect the fluorescence of the microbes with a sensitivity to 1 cell per cubic centimeter. Such a device, they said, will be installed aboard a Mars rover to detect life on the red planet in the future.

Source: Xinhua News Agency - CEIS

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