Mars is a very mysterious planet in the eyes of the ancients, and the ancient continent called it "Ying confusion", believing that the celestial phenomenon "Ying Confusion Guarding The Heart" heralded an ominous occurrence. Western countries regard the red color of Mars as a symbol of blood, so they are named after Mars, the god of war in Greek mythology.
Now, this "brother" planet of the earth has become a fascinating place, and whether there is possible (ever) life on Mars is a major concern for all mankind. With the development of modern science and technology, since the 1960s, human beings have successively carried out 51 Mars exploration missions, until the Chinese "Tianwen-1" and the American "Perseverance" in 2021. These missions are undoubtedly the most direct means of conducting research on the evolution of the habitable environment and life exploration on Mars.
In addition, there are many areas on Earth that can be compared to the past or present environmental, geological, mineral and other conditions of Mars, called Mars-like regions. The "dry pole" Atacama Desert in northern Chile, South America, is considered a very typical Martian-like environment on Earth because of its extreme drought, high radiation, and high salinity environmental characteristics.[1] The Mars scene from the 2004 British science fiction documentary "Interstellar Odyssey" was filmed here.
Figure 1 Mars and the Atacama Desert in South America (coinciding with Mars in the figure)[2]
The Atacama Desert runs through western South America, and its arid zone is located in a vast space of about 1,000 kilometers at 20 to 30 degrees south latitude. Although the Atacama Desert is adjacent to the Pacific Ocean, it is separated by the Western High-Altitude Coast Mountains and the Eastern Andes Mountains, creating a "sandwich" structure that prevents moisture from eastern and western sources from reaching the central area. At the same time, rainfall was scarce on the west coast of Chile due to the inversion caused by the Pacific anticyclone and the Peruvian Cold Snap[3]. These processes lasted tens of millions or even hundreds of millions of years, resulting in the gradual accumulation of drought levels in the region into what is now a desert region .[4,5] The Atacama Desert can be analogous not only to the surface environment of modern Mars, but also to its geological evolution from wet to arid about 3 billion years ago to mars' transition from the humid Western to the dry Amazon.
Figure 2 Valley of the Moon in the Atacama Desert[6]
The Atacama Desert receives less than 20 millimeters of annual rainfall and rises from a few hundred meters to about 5,000 meters above sea level, and although it is not as hot as most deserts, the day-night temperature change can drop from 22 °C to -2 °C. Because clouds and mist are difficult to cross the rolling mountains, moisture collects in the higher elevation of the mountain, so that the region has a unique phenomenon of higher altitude and higher humidity, this unique humid fog in South America is called "thick wet fog".
Figure 3 Thick wet fog at high altitude[7]
The Atacama Desert is located in a depression in the middle of the Coast Mountains and the Andes Mountains, with little cloud cover, so it receives a high dose of ultraviolet light, with UV B-bands that can cause sunburn on human skin 1.4 times higher than in the deserts of northern Africa.[8] Strong ultraviolet radiation induces the reaction of ozone and nitrogen or chloride in the atmosphere, producing strong oxidizing nitrates or perchlorates, which accumulate gradually on the surface of the Atacama Desert as the atmosphere settles, and rainfall is scarce in the desert, so large amounts of nitrate and perchlorate can be enriched on the surface of the Atacama Desert [9].
Figure 4 Flat area in the Atacama Desert[10]
The core arid region of the northern Atacama Desert is an endless stretch of pale yellow sand that is the nightmare of most life. Desert flowering can occur in the slightly moister parts of the southern desert after occasional rainfall in the spring, and common plants in the area include salt grass, thyme and tight eagle parsley. Some scientists speculate that this phenomenon may have also occurred in the early mars transition from a humid environment to an extremely arid modern environment.
Fig. 5 A stunning view of the flowering phenomenon in the southern part of the Atacama Desert[11]
The vast Atacama Desert is an excellent area for astronomical observation with dry air, clear, cloudless, far from the city, and virtually no light pollution or radio interference. The United States, Canada, Germany, the United Kingdom, France, and Japan have all built observatories and telescopes at high altitudes here, such as the famous Atacama Large Millimeter-Submillimeter Wave Radio Telescope Array (ALMA). At night, Atacama is full of stars, and thousands of stars are clearly visible, which is very romantic.
Figure 6 Observation of the Milky Way by the ALMA telescope in Chile[13]
The Atacama Desert is a payload and equipment test area for many Mars exploration missions, and tests such as NASA's Viking and Phoenix have also undergone ground-based repeated studies in the Atacama Desert, and this area is also an important site for NASA's Earth-Mars Cave Exploration Program.
The Atacama Desert, as a very typical Martian-like environment on Earth, has raised human awareness of Mars.
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| Shen Jianxun, Lin Wei
| Wang Wanyu
Proofreading | Zhang Tengfei Jiang Xuejiao