Atacama Desert

It takes more than just one mountain range to maintain the amazing Atacama Desert. A number of land features and weather factors converge in this unique location. The first, of course, is those Andes. Atacama is in this mountain range’s rainshadow, an area of a mountain downwind of the general prevailing winds. This means that when winds and moist air hit the mountain on one side, that air condenses into a lot of rain. But that leaves the air dry as it tops the mountain and proceeds to the other side. As if the Andes aren’t enough, rain is blocked on the other side by the Chilean Coast Range. The anticyclone in the Pacific, a reverse spin area of very dry air, contributes on top of the rain shielding mountains.

The results are startling. The Atacama Desert receives about 1 millimeter of rain a year. Some areas never receive rain. There is also evidence that the entire region was completely rain free from about 1570 to 1971. Is that a drought? Can there be a drought in an area that received less rain in a year than a thimble would hold? There are some river beds in the desert that haven’t held any water for at least 120,000 years.

The Atacama Desert does gain some fame from its dry conditions. Scientists have compared conditions there, including soil conditions, to conditions on Mars. In fact, it’s been a stand in for Mars in many movies including documentaries and fiction. In 2003 some scientists decided to conduct the same tests that the Mars landers, Viking 1 and Viking 2, had conducted on the red planet. The purpose of those tests was to detect life. What was the verdict? There were no signs of life in the Atacama Desert. Now this waterless desert is used for further research and even tests to prepare for future missions to Mars.

Next time you’re thirsty, consider life in the Atacama Desert. Forget a lemonade stand. In one of the driest places on Earth it could be years before you could even fill a small glass with water.

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