Refuge from its own world
The current Martian surface environment is extremely hostile to any known form of life, said Carlton Allen, an astrobiologist and curator of astromaterials at the NASA Johnson Space Center in Houston, Texas.
On Mars, a wicked combination of subfreezing temperature, low atmospheric pressure and high ultraviolet flux, combined with dried out and possibly oxidizing soil, makes it tough for even the hardiest microorganisms to survive, Allen said.
But Martian life may be a refuge from its own world, lurking in safe havens on the planet. Here on Earth, microbial life has been detected in hydrothermal systems, lakes, caves and subsurface aquifers. On Mars, one of those havens might be the planet's polar caps.
Polar caps: life on ice?
Allen is part of a research team studying the evidence for microbiology in Earth's glaciated polar regions as analogs to the polar caps of Mars.
Earth's polar deserts, particularly in Antarctica, are some of the least hospitable places on this planet for life's survival and growth. "But in the harshest polar climes that you can find on Earth there is still a small amount of either present or recent past life," Allen told SPACE.com .
"If we are going to look for life on Mars," Allen said, "one of the places we may want to look is in the polar regions.
Mars polar icecaps could be among the sites most likely to preserve evidence of life on Mars, Allen reported at the conference.
Unofficial record-keeper
Windblown dust, carrying material from locations across the entire planet, forms recognizable layers in the ice. Microorganisms transported to the poles on this dust could be trapped and protected from the hostile surface environment. It may be possible that the ice is the unofficial record-keeper of Martian life through time, he said.
"That dust comes from everywhere on the whole planet. It puts whatever it's carrying into deep freeze suspension," Allen said.
Bacteria can be preserved in ice for millennia, Allen and his fellow researchers reported. Furthermore, recognizable forms of bacteria remain for hundreds of thousands of years and identifiable DNA is preserved for at least 1,800 years. A portion of these bacteria can be cultured after more than 1,000 years in the ice.
In some cases a subset of the bacteria continues to metabolize within the snow, and some bacteria in ice may remain viable for hundreds of thousands of years.
Little oasis of life
Allen and his colleagues have also studied glacial springs in Arctic Canada. Ice sheets and glaciers in the arctic also represent extremely challenging environments for life's survival and growth.
The researchers recently trekked to northern Ellesmere Island, Canada. Glacial springs there contain evidence for a complex community of subsurface bacteria existing within or beneath a thick sheet of glacial ice.
Allen said that there are sulfur-depositing warm springs percolating up through 660 feet (200 meters) of glacial ice on the island -- a rare occurrence here on Earth. Different types of microorganisms in fairly high abundance were found.
"What we're saying is in this vast almost sterile polar environment, here is this little oasis of life," Allen said.
On Mars, finding spots where ice is being melted by underground heat would be a primary kind of place to study. "If Mars has a subsurface biosphere, you would have evidence being brought to the surface," he said.
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