The Atacama, which stretches 600 miles (1,000 kilometers) from Peru's southern border into northern Chile, is what climatologists describe as an absolute desert. It is filled with sterile, bone-dry stretches where rain has never been recorded for as long as humans have been measuring the weather. As a result, much of this parched area is totally devoid of vegetation [source: Vesilind].
With features such as sand dunes and lava flows, it's not hard to imagine the Atacama as being similar to the landscape that robotic probes — and someday, astronauts — would find on Mars. That's one reason that NASA has used the Chilean desert as a test site. In 2005, for example, a NASA probe detected microbial life in the Atacama's seemingly barren soil, as scientists are hopeful that they'll also be able to do on Mars [source: NASA].