Why Astronomers Love the Atacama Desert

NASA's rover in the Atacama Desert
This picture might look like NASA's rover is on Mars, but in fact, it's in the Atacama Desert in Chile. The desert's environment is similar to that of the red planet, making it an ideal testing ground for missions. NASA/CampoAlto/V. Robles

If asked to point out the world's greatest deserts, you can probably identify the Sahara on a map, and perhaps one or two of the deserts in North America (there are four)! But can you name the driest desert — possibly the driest place on Earth?

That would be the Atacama Desert, which lies in northern Chile, stretching about 700 miles (1,127 kilometers) and around 49,000 square miles (126,909 square kilometers) in area. It is home to very little life — unless you count the scientists and researchers that have found it to be an incredible laboratory for studying space and one of our planetary neighbors.


The Driest Place on Earth

One of the things that makes the Atacama unique, even among deserts, is how long it has been so dry. The Atacama is the oldest desert on Earth and has been semiarid for an estimated 150 million years; the driest part of the desert receives only one-fiftieth of the annual precipitation that Death Valley receives, on average.

This is in part due to the geographic location — and formations — around the Atacama Desert, which has the Andes Mountains on the east and the Chilean Coastal Range on the west, creating a double "rain shadow" where very little precipitation ever falls. Despite this lack of rain, the Atacama is also quite cool. Unlike more stereotypical deserts — like the Saraha — where triple-digit temperatures are the norm, the average temperature ranges between lows in the 30s and highs in the 70s (Fahrenheit), or 0 to the 20s in Celsius.


This might seem like a strange combination of factors, but it has its benefits. Virtually no rain and cool temperatures create a unique ecosystem that has long inspired scientists to explore the life (or lack thereof) in the Atacama — and consider what it might mean for life on other planets too. Unlike other deserts, there are no cacti, insects or even pathogens in some parts of this plain.

How the Atacama Resembles Mars

NASA camp in the Atacama Desert
Once a year, NASA's Atacama Rover Astrobiology Drilling Studies team plants its tents in the desert to test a prototype rover, several life-detection instruments and methods scientists might use on a future mission to the red planet. (The dead trees are leftover from an irrigation study done by a local college.) NASA/Ames Research Center

With the exception of a deluge of rain in early 2019, the Atacama Desert has been an excellent proxy for organizations like NASA to try and understand what Mars might be like — with a breathable atmosphere, of course. NASA has long used the Atacama as a testing ground in trying to find examples of the small, microbial life that call this desert home and extrapolating how that might be used to detect life on Mars. It has also been a helpful environment for testing Mars rover designs since 1997.

One thing that scientists love about the Atacama is that, thanks to its remoteness, there are no local settlements and virtually no tourism/business infrastructure in the area, which helps reduce contamination of experiments. (There are, however, many tours offered to the Atacama, both for stargazers and adventure enthusiasts.)


Why So Many Radio Telescopes Are Here

Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope
The Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope in the Atacama Desert, Chile, celebrated 10 years of operation on March 13, 2022. ALMA is made up of 66 high-precision antennas, which together act as a single telescope, currently the largest radio telescope in the world. Lucas Aguayo Araos/Anadolu Agency via Getty Images

Part of the Atacama has become home to a series of exceptionally powerful Earth-based telescopes, including the composite Very Large Telescope (comprising four 27-foot or 8-meter scopes) and the Vera C. Rubin Observatory, another 8-meter scope that is set to begin operations in late 2024.

The conditions that make the Atacama perfect for Mars research also apply to other space-related studies: A lack of humidity or moisture makes for incredibly low distortion in the view skyward, and no light pollution ensures that the only light these lenses capture comes from whichever distant galaxy or star it is gazing toward. Additionally, being located nearer to the equator than other large telescopes gives each facility the chance to observe much more of the night sky, including our home galaxy and far beyond.