Atacama Desert

South America’s Atacama Desert is dry. It’s the second driest desert in the world, after the McMurdo Dry Valleys of Antarctica. It’s been a desert for over 20 million years, kept that way by the Andes Mountains which block rain from reaching the area. Death Valley California has a reputation for being dry. But Atacama is 50 times as dry.

Atacama Desert

It’s not only the Andes keeping the Atacama Desert dry. There are other geographic features and weather factors at work here. But let’s consider the 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 that’s not bad enough, the Chilean coast range is responsible for the same effect on the opposite side of the desert. The anticyclone in the Pacific, a reverse spin area of very dry air, contributes on top of the rain shielding mountains.

It’s so dry its stunning. Rain falls in the Atacama Desert to the tune of only about 1 mm every year. Some places in the desert never receive rain. Meteorologists also believe that a complete drought, no rain at all, began in 1570 and lasted 400 years. Is that a drought? How can there be a drought were it barely rains in the first place? 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. The soil and overall conditions are very similar to what it’s like 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. These tests determined whether or not there was life on Mars. Can you guess the results? Like Mars, the Atacama Desert had no life. So scientists now use this desert to prepare future tests for the red planet.

Atacama Desert

When you drink a glass of water think about the Atacama Desert. Drinks are not served there. In one of the driest places on Earth it could be years before you could even fill a small glass with water.