The Atacama Desert, a place on Earth most similar to Mars, stretches along the west coast of South America, covering parts of northern Chile, Peru, Bolivia, and Argentina. However, its core arid zone is primarily concentrated in Chile. This desert is widely recognized as the closest terrestrial environment to Mars, making it a prime location for scientists and space agencies to conduct Mars environmental simulation experiments.
This region is the driest non-polar area on Earth, with some areas receiving less than 1 millimeter of annual precipitation. In fact, there are weather stations that have recorded decades without a single drop of rain. The extreme aridity mirrors the lack of liquid water on the Martian surface. Ancient river traces have been discovered on Mars, but the planet is now extremely dry.
The dried-up salt lakes, such as Salar de Atacama, and ancient riverbeds in the Atacama provide valuable analogs for studying the water history of Mars.
The soil in the Atacama is rich in strong oxidizing compounds like sulfates and perchlorates, similar to the components detected by Mars rovers, such as Curiosity, in Gale Crater. These compounds are toxic to microorganisms, indicating that both environments are inhospitable to life. Due to the scarcity of water, rock weathering is slow, and the surface is covered with a large amount of undecomposed debris, much like the regolith on Mars.
At an average altitude of over 2000 meters, the Atacama has thin air and intense ultraviolet radiation, comparable to the conditions on Mars, where the thin atmosphere allows stronger penetration of UV light. Scientists use this high-radiation environment to study the tolerance of life under extreme conditions. NASA has tested prototypes of Mars rovers here, simulating their performance in low-pressure environments.
Despite the harsh conditions, extremophile microorganisms still thrive in the Atacama. For example, cyanobacteria in underground salt layers survive by capturing trace amounts of water molecules using hygroscopic salts. This suggests that similar life forms may exist in the subsurface or salt rocks of Mars.
Scientists also test the sensitivity of life detection instruments here. A 2019 study found that current equipment might miss some microorganisms in the Atacama, highlighting the need for more advanced technology in Mars exploration.
The widespread sand dunes and wind-eroded rock formations in the Atacama bear a striking resemblance to the dune fields on Mars, such as those in Jezero Crater, explored by the Perseverance rover. Volcanic terrains, like Licancabur volcano, and dry salt lakes (Salars) in the desert are analogous to ancient volcanic activity and ancient lake relics on Mars.
The “ARADS” project tests Mars agricultural technology in the Atacama, attempting to grow crops in simulated Martian soil. The European Space Agency (ESA) also uses this area to validate Mars sample collection strategies and drone exploration technologies, further cementing the Atacama’s role as a crucial testing ground for future Mars missions.
Due to its exceptionally dry and clear conditions, the Atacama Desert stands out as one of the premier astronomical observation sites in the world, home to several international observatories, including the renowned ALMA. This unique environment has become a focal point for Mars exploration, with researchers drawing parallels between the desert and the Red Planet.
The Atacama’s extremely arid climate, Martian-like soil composition, intense radiation, and otherworldly landscapes make it an unparalleled “natural laboratory” for studying Martian geology, climate, and the potential for life. Despite the harsh conditions that make survival challenging even for Earth’s hardiest organisms, the Atacama offers a critical and irreplaceable window into the possibilities of extraterrestrial life and future human colonization of Mars.
