CORVALLIS, Ore. - Bacterial colonies are thriving underneath ice on one of the coldest, driest deserts on Earth, researchers have discovered, in conditions that might compare to those on Mars or Europa and provide insights for life forms that could be found elsewhere in our solar system.
The study will be reported Friday in the journal Science.
This study was conducted on ice-covered lakes in the McMurdo Dry Valleys of Antarctica, which has an average annual temperature about 68 degrees below zero and gets less than four inches of precipitation a year.
But in that frigid, arid environment, scientists at Oregon State University and four other institutions found liquid water pockets embedded about six feet deep in solid ice, where a combination of sediments, water and solar radiation during long summer days supports a viable population of bacteria.
"This is a very barren environment with virtually nothing we usually associate with living organisms," said Stephen Giovannoni, an associate professor of microbiology at Oregon State University. "But these photosynthetic cyanobacteria are alive, self-sufficient, and growing. They're able to live through the harsh freeze-thaw cycle of the seasons, fix nitrogen and release oxygen as they make carbohydrates from water.
"They have their own little world there we knew nothing about."
The nutritional requirements of these life forms are minimal, Giovannoni said - a little light, water, phosphate, nitrate and other minerals. But in fact the primitive life processes they are undertaking are quite similar to those that first formed the oxygen-rich atmosphere of Earth and made higher life forms possible.
And in the study, the researchers cite two locations where they feel conditions may exist that are similar to those found in barren Antarctica - Mars, and a large moon of Jupiter, Europa.
"It's been suggested that Mars is too dry and cold for life to exist," Giovannoni said. "But it's also known that both Mars and Europa have frozen water on or near their surfaces. We speculate that in conditions similar to those we observed in Antarctica, it would be a distinct possibility that similar life forms exist on Mars or Europa."
While Mars may have had extensive liquid water at one time, the researchers say in their report, it rapidly cooled and ice would have become, as it is today, the dominant form of water on Mars' surface. A search for fossil evidence of the most recent life on Mars' surface could be based on life within ice, they said.
The process of life formation is still largely unknown and very complex, Giovannoni said.
"Any cell, even a very basic cell such as those found in bacteria, is a very complicated thing," he said. "But experiments have shown you can get fairly complicated molecules and amino acids from the interaction of basic chemicals and electricity."
Giovannoni has studied bacteria all over the Earth, from the basalt rocks of deep sea floors to Antarctic ice cores, Yellowstone National Park hot springs and the bacterial plankton of Oregon's Crater Lake. Researchers continue to be amazed, he said, at how little is known about microbes, how few have actually been described, how they function and their ecological interaction with the rest of the world.
"Recent advances in molecular biology now allow us to identify these unknown organisms, and what we're learning is the world is full of bacteria we know virtually nothing about," he said. "I could probably isolate a new, previously unknown bacterium from the sole of your shoe."
Past research has been held back by lack of funding, Giovannoni said, as agencies seemed unsure that studies of bacteria, their evolution or behavior had any practical value. But new applications of bacterial research in understanding the global carbon cycle, creating new antibiotics or enzymes for industrial use have raised increasing interest, he said.
And the search for life elsewhere in the universe might first be successful, he said, when bacteria such as those being identified in Antarctica are one day found on Mars.
Stephen Giovannoni, 541-737-1835
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