The Atacama is the driest desert on Earth. Previous studies were able to find microbes in the wetter portions on the desert. However samples taken from the drier central region showed no detectable microbes.
This had been taken to explain the Viking "no life" results:
Mars-Like Atacama Desert Could Explain Viking No Life Results.
Moffett Field - Nov 10, 2003
Dry Limit of Life
"Extreme Life Summary (Jan 15, 2004): Among the triad of biological limits to life on Mars--cold, thin air and dryness--a new study in the driest place on Earth reveals a remarkably sterile crucible for testing instruments that might one day answer questions about microbial life on other planets. The Atacama desert in Chile, when probed with some of the same techniques used during the 1976 Viking mission, found no life on Earth, a finding that may help scientists understand the dry limits to life and the potential importance of site selection."
However, two separate studies have now found that microbes exist even in the driest parts of the Atacama:
Deliquescence in the Atacama.
Date Released: Monday, July 10, 2006
"While strolling through the salar, Wierzchos noticed a thin dirty gray layer along the edge of one of these salt rocks, a few millimeters (about one-quarter of an inch) below its surface. Intrigued, he broke off a piece of the rock and brought it back to the research station. He dissolved a bit of the material in water, placed a drop on a microscope slide, and took a look. He expected it to be some kind of mineral contamination.
"Instead, what he saw were living cells. There was life, thriving, inside dry salt rocks. He had discovered a previously unknown habitat for life on Earth. Microbes had been discovered living in rocks before. And they'd been found living in extremely salty - wet and salty - environments. But never inside dry salt rocks.
"In wet halite, okay,' says Wierzchos, citing the Dead Sea as an example of a wet, salty environment where microbes have been found. 'But this is dry halite. This is totally different stuff."
A Preliminary Survey of Non-Lichenized Fungi Cultured from the Hyperarid Atacama Desert of Chile.
Date Released: Tuesday, August 22, 2006.