Facts about Atacama Desert, South America - A resemblance to Mars

Chile's Atacama Desert, which stretches from the Pacific Ocean to the Andes Mountains, is a sparsely populated, almost rainless plateau. It is less than 100 miles wide on average, yet it stretches 600 miles south of the Peruvian border. The Pacific Coastal Range, with an average elevation of 2500 feet, is the mountain range closest to the ocean. East of the Andes Mountains is the Cordillera Domeyko, a range of foothills. Salt basins (salars), sand, and lava flows make up the Atacama. The scenery is regarded as "moon-like" since it is so bleak. In reality, the Atacama Desert has been considered as a suitable location for testing a future lunar rover prototype.

Figure 1 (a) Current climatic zones of western South America. SA stands for Salar de Atacama.(b) Morphotectonic subdivisions of the Central Andes.

Geology & geochemistry

The Atacama Desert, the world's driest, has a number of geological and geochemical characteristics that set it apart from any other habitat on the planet. Its climate has been defined as arid to hyperarid for at least the previous 10 million years, given its location on the western border of South America, between 17 and 28 °S. The Atacama Desert's dry climatic conditions have been linked to Andean uplift and are thought to have influenced the development of the desert's most distinctive features, such as (i) nitrates and iodine deposits in the Central Depression, (ii) secondary enrichment in porphyry copper deposits in the Precordillera, and (iii) Li enrichment in salt flats of the Atacama. The Atacama Desert's geology and physiography have been substantially formed by the convergent margin that has existed since the Mesozoic epoch. In addition to anthropogenic activities, the geochemistry of surface materials is linked to rock geochemistry (Co, Cr, Fe, Mn, V, and Zn), salt flats, and evaporite compositions in endorheic basins (As, B, and Li) (Cu, Mo, and Pb). Surface water has a wide range of compositions, although in general it has a circumneutral pH and higher conductivity and total dissolved solids than brines. With the exception of HCO3-, major water constituents are generally related to increased salinity, and despite the fact that trace elements are not well-documented, surface waters of the Atacama Desert are enriched in As, B, and Li when compared to average respective concentrations in the rivers of the world (J Tapia et al., 2018).

Figure 2 Geomorphological and geological sections of Atacama desert (Risacher et al., 1999).

Figure 3 Hydrogeochemistry of Atacam basin.

Driest desert in the world

NASA research has determined that this desert in northern Chile is the driest desert on the planet. In the Atacama, several weather stations have never seen rain. In Chile's central sector, which is defined by the cities of Antofagasta, Calama, and Copiapó, there have been periods of up to four years without rain. Evidence implies that there was no major rainfall in the Atacama Desert between 1570 and 1971.

Figure 4 Atacama desert - the driest desert in the world. 

Desert with no rainfall

The average annual rainfall in this area is roughly 1 mm. Some parts of the desert have never received any precipitation. Arica and Iquique, for example, receive 1 to 3 mm (0.04 to 0.12 in) of rain per year. The Atacama's aridity is explained by its location, which is sandwiched between two mountain chains (the Andes and the Chilean Coast Range) of sufficient height to block precipitation advection from either the Pacific or the Atlantic Oceans, creating a two-sided rain shadow.

Figure 5 The dry air towards the pointed tip of the desert is the indication of little or no rainfall in this region.

Sterile surface

The Andes Mountains and the Chilean Costal Range, which encircle the Atacama Desert, restrict rainfall, making it a kind of death zone for plants, depriving the land of water and nutrients.

Home of sodium nitrate in the world

This region has the world's largest natural supply of sodium nitrate, which may be used to make fertilizers, explosives, and other products. In the 1940s, mining for this mineral, sometimes known as Chile saltpetre, was booming, and several abandoned mining communities can be seen and visited in the desert.

Figure 6 (a) Presence of sodium nitrate deposits in the rock layers (d) Presence of fresh water. Credits: Ji-Hye Seo

Extra terrestrial soil

Because the soil samples from this location are strikingly similar to those from Mars, NASA utilizes it to test instruments for trips to the red planet. The NASA-funded Earth-Mars Cave Detection Program uses the Atacama as a test location. The Atacama has also been utilized to film scenes set on Mars, most notably in the TV series Space Odyssey: Voyage to the Planets.

Extreme temperatures

Temperatures in the desert can reach 40 ℃ (104 degrees Fahrenheit) during the day and 5 °C (41 degrees Fahrenheit) at night. Throughout the year, the weather is beautiful, with more than 90% of the days being sunny. Each month, there is an amazing moon for 10 to 12 nights, and you may appreciate the blackness of the night with its pure air and lack of clouds, which allows the stars to shine like no other place on earth.

Chinchorro Mummies

In the Atacama Desert, the earliest artificially mummified human remains have been discovered. These mummies are thousands of years older than Egyptian mummies, and the absolute lack of moisture aids in their preservation. To put this in context, the oldest mummy discovered in Egypt dates back to roughly 3000 BC, whereas the oldest mummy discovered in the Atacama Desert dates back to around 7020 BC.

Figure 7 Remains of Chinchorro mummies found at Atacama deserts.

Presence of snow

Despite the fact that this is the world's driest desert and high temperatures throughout the day, the high peaks are covered in snow. This is feasible because to the altitude, which prevents temperatures in these areas from rising significantly.

Figure 8 Snow indication at the northern part of Atacama desert.

Astronomical Observations

The Atacama Desert is one of the few places on the planet with 300+ days of clear sky a year, no light pollution, and a high altitude, making it perhaps the best location for observatories in the world. In recent years, the desert has become home to ALMA, the world's largest ground telescope, where scientists study the birth of stars using images taken by 66 radio telescopes.

Figure 9 Atacama's largest ground telescope - (ALMA).

Comparison to Mars

The soil in an area around 100 kilometers (60 miles) south of Antofagasta, with an average height of 3,000 meters (10,000 feet), has been compared to that of Mars. The Atacama has been used for filming Mars scenes, most notably in the television series Space Odyssey: Voyage to the Planets, due to its unearthly aspect. In 2003, a group of academics produced a paper in which they replicated the procedures used by the Viking 1 and Viking 2 Mars landers to identify life and found no indications of life in the Atacama Desert soil of the Yungay region. 

In this way, the location may be unique on Earth, and NASA is using it to test instruments for future Mars expeditions. The researchers replicated the Viking tests in Mars-like Earth conditions and discovered that they missed traces of life in soil samples from Antarctic dry valleys, Chile's and Peru's Atacama Desert, and other locations. However, in 2014, a new hyperarid site, Mara Elena South, was discovered, which was even drier than Yungay and thus more Mars-like.

Figure 10 Comparison of Mars surface and Atacama desert surface. Credits: NASA/JPL-Caltech/ASU