Earth microbes may be able to survive on Mars, US study finds

2013-01-11 02:37:51 GMT2013-01-11 10:37:51(Beijing Time)  SINA.com
Photo of Mars (Photo/File)Photo of Mars (Photo/File)

A hardy bacteria common on Earth was surprisingly adaptive to Mars-like low pressure, cold and carbon dioxide-rich atmosphere, a finding that has implications in the search for extraterrestrial life.

The bacteria, known as Serratia liquefaciens, is found in human skin, hair and lungs, as well as in fish, aquatic systems, plant leaves and roots.

"It's present in a wide range of medium-temperature ecological niches," said microbiologist Andrew Schuerger, with the University of Florida.

Serratia liquefaciens most likely evolved at sea level, so it was surprising to find it could grow in an experiment chamber that reduced pressure down to a Mars-like 7 millibars, Schuerger said.

Sea-level atmospheric pressure on Earth is about 1,000 millibars or 1 bar.

"It was a really big surprise," Schuerger said. "We had no reason to believe it was going to be able to grow at 7 millibars. It was just included in the study because we had cultures easily on hand and these species have been recovered from spacecraft."

In addition to concerns that hitchhiking microbes could inadvertently contaminate Mars, the study opens the door to a wider variety of life forms with the potential to evolve indigenously.

To survive, however, the microbes would need to be shielded from the harsh ultraviolet radiation that blasts the surface of Mars, as well as have access to a source of water, organic carbon and nitrogen.

NASA's Curiosity Mars rover is five months into a planned two-year mission to look for chemistry and environmental conditions that could have supported and preserved microbial life.

Scientists do not expect to find life at the rover's landing site - a very dry, ancient impact basin called Gale Crater near the Martian equator. They are however hoping to learn if the planet most like Earth in the solar system has or ever had the ingredients for life by chemically analyzing rocks and soil in layers of sediment.

So far, efforts to find Earth microbes that could live in the harsh conditions of Mars have primarily focused on so-called extremophiles which are found only in extreme cold, dry or acidic environments on Earth. Two extremophiles tested along with the Serratia liquefaciens and 23 other common microbes did not survive the experiment.

A follow-up experiment on about 10,000 other microbes retrieved from boring 12 to 21 meters into the Siberian permafrost found six species that could grow in the simulated Mars chamber, located at the Space Life Sciences Laboratory adjacent to NASA's Kennedy Space Center in Florida.

The next step is to see how the microbes fare under even more hostile conditions.

(Agencies)

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