Such an environment, say the researchers, is similar to what Mars was like 3.5 billion years ago when, according to morphological evidence, icy lakes and rivers covered the red planet.
"This is probably the best analog in the world," said Cabrol, who with her colleagues performed a preliminary reconnaissance of the region in 2002. The scientists will visit the lakes each year through 2008.
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On the 2002 trip, the researchers discovered abundant and diverse life-forms thriving in the lakes in and around Licancabur, raising speculation that life could have existed on ancient Mars.
In addition, two billion years ago, there was no ozone layer protecting Earth from harmful ultraviolet rays. Thus the life forms that thrive in these lakes are like a window back into time when life first evolved on Earth.
"We are looking at our own past to see how we made it," said Cabrol.
These high lakes on the altiplano, a high-altitude desert that is one of the world's driest regions, are what scientists refer to as extreme environments and the microbes that live in the lakes are called extremophilesorganisms that love living on the edge.
Such life-forms fascinate scientists. To survive in extreme environments the organisms must evolve unique traits and scientists keep looking in more and more extreme environmentshydrothermal vents, underwater caves, volcanoesto understand the limits of life on Earth.
"So far, we have not found a limit of life," said Cabrol. "But these lakes might show a limit."
Last year, the researchers discovered very small plankton-like algae called diatoms that had ten times more deformities than similar algae in other lakes. The researchers believe that the intense ultraviolet radiation on the altiplano is finally catching up to the organisms.
These lakes lie on the eastern edge of the world's driest desert, the Atacama, and they are evaporating. The deformed diatoms were found in a lake at the foot of Licancabur that is now just 1.5 feet (50 centimeters) deep. Harmful ultraviolet rays can penetrate water up to 3 feet (1 meter).
"The question is now, are these deformations mutations towards adaptation or are they the sign that life cannot cope in the environment and they are going into extinction," said Cabrol.
The team will set up data collection stations with instruments and experiments to measure ultraviolet radiation and its effect on life in the area. Whether the diatoms are on the road to extinction or evolving a sort of UV sunblock, Cabrol's interested.
"On the one hand, we may see how life may be able to adapt itself against UV and strategies for UV on other planets. On the other hand, we may be finding a real limit of life on Earth," she said.
The Licancabur Expedition is funded by grants from the National Geographic Society, NASA, the SETI Institute, and the support of other organizations.
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