Atacama Desert

• 1. Introduction

  ›

  The Atacama Desert, a plateau on the Pacific coast of South America, contains weather stations that have never recorded a single drop of rain. Evidence suggests that no significant rain fell across much of it from 1570 to 1971, a stretch of roughly four centuries. The desert runs for about 1600 km along northern Chile, in the shadow of the Andes. Its surface covers some 105000 square kilometers, and more if the barren lower slopes of the mountains are counted. Why does so little water reach this land, and how old is the dryness? What manages to live here, and who has tried to make a home on it? And why do astronomers and space scientists treat this strip of rock and salt as a kind of laboratory?

  37182329

• 2. The Double Rain Shadow

  ›

  Two mountain ranges stand guard over the Atacama: the Andes to the east and the Chilean Coast Range to the west. Both are tall enough to stop moisture from crossing, whether it comes off the Pacific or drifts in from the Atlantic. Geographers call this a two-sided rain shadow. The cold Humboldt Current, flowing north along the coast, and a high-pressure system over the South Pacific make the effect stronger still.

  The average rainfall is about 15 mm a year, but some locations receive only 1 to 3 mm. The driest ground is usually placed around the abandoned mining town of Yungay, in the Antofagasta Region, where the University of Antofagasta runs a desert research station. In the central sector, between the cities of Antofagasta, Calama and Copiapó, records show stretches of up to four years with no rain at all.

  Heat is not the story here. By the Köppen classification the Atacama counts as a cold desert, with mild temperatures all year and only slight differences between seasons. The missing rain is what defines it.

  The dryness reaches into the sky. Many mountains higher than 6000 m carry no glaciers at all, and only the tallest peaks hold permanent snow. Ojos del Salado and Monte Pissis are named among them, and Llullaillaco is listed with a debatable claim. In the southern part, between 25 and 27 degrees south, glaciers may have been absent even during the ice ages. Permafrost still extends down to 4400 m and is continuous above 5600 m.

  When rain does arrive, the ground cannot cope. In June 1991, unusual rainfall around Antofagasta, Taltal and inland toward Calama sent mudflows down the slopes that killed 91 people. On the 25th of March 2015, floods in the southern desert brought mudflows into Copiapo, Tierra Amarilla, Chanaral and Diego de Almagro, and more than 100 people died. In early 2019, extreme heat and wildfires in Chile were followed by heavy flooding in the Atacama, which killed at least 6 people and destroyed 346 homes.

  39184149

• 3. Deep Time

  ›

  About 33 million years ago, the Tasmania-Antarctic passage opened, and the planet's oceans changed course. Cold currents began running along the west coast of South America. That cooling cut off the warm, humid air that had once traveled from the Amazon Basin toward the Atacama, and a proto-Humboldt current took shape. The desert has experienced extreme dryness since at least the Middle Miocene, which is why some researchers think it may be the oldest desert on Earth.

  The record is not perfectly flat. Between about 10.86 and 6.4 million years ago, humidity rose enough to sustain the Tiliviche Palaeolake, which later became a salt flat sometime before the Middle Pliocene. In some sections, evaporite formations suggest that arid conditions have held for as long as 200 million years, back to the Triassic.

  Scientists still argue about what caused the extreme dryness. The desert's aridity predates the rise of the Central Andes, yet the hyperarid state is generally thought to come from that rise. Before the mountains grew, the climate is hypothesized to have resembled that of the Namib Desert. Meanwhile, a group of British scientists has suggested that some river beds here have been dry for 120,000 years.

  The modern picture of a land without plants is also incomplete. A large flatland called the Pampa del Tamarugal was once a woodland, in pre-Columbian and colonial times. Demand for firewood from silver and saltpeter mining in the 18th and 19th centuries led to widespread deforestation.

  2426271329

• 4. Life on Fog

  ›

  The word camanchaca names a marine fog that rolls in from the ocean across parts of the Atacama. It supplies enough moisture for algae living under stones, for lichens, and even for some cacti, with the genus Copiapoa the best known. More than 500 plant species have been gathered within the desert's borders. Herbs and flowers such as thyme, llareta and saltgrass are the most common. Where humidity allows, trees appear, including the tamarugo, which grows only in the Atacama, along with the chañar, the pimiento tree and the leafy algarrobo.

  The llareta shows how far a plant can go to survive. It grows at altitudes between 3,000 and 5,000 m, in a dense cushion 3 to 4 m thick. The cushion captures heat during the day and holds it against the cold evenings. Growth is slow, estimated recently at 1.5 cm a year, so many llaretas are more than 3,000 years old. Its resin was prized, and the mining industry once harvested the plant for fuel without restraint, which left it endangered.

  Some cacti grow tall. The cardon and candelabro can reach 7 m in height and 70 cm across. In years with enough rain, the desert flowers between September and November, a display called the desierto florido that occurred in 2015.

  The animal list is shorter. Parts of the desert are so dry that neither plants nor animals survive. Elsewhere, sand-colored grasshoppers blend into the pebbles, and red scorpions live in the open ground. In the lomas, the fog-fed hills, beetles and their larvae feed other animals, and the Vallenar toad lays eggs in permanent ponds or streams. Few reptiles live here, though one lizard, Liolaemus fabiani, is found only in the Salar de Atacama salt flat.

  Birds are among the most varied animals. Humboldt penguins live year-round along the coast and nest in cliffs above the ocean. Andean flamingos use the high salt flats, while Chilean flamingos stay near the shore. The lomas feed visiting hummingbirds and help sustain the endangered Chilean woodstar.

  Darwin's leaf-eared mouse is one of the few specialized mammals. In the less arid areas live the South American gray fox and the viscacha, a relative of the chinchilla. Vicuñas stay close to steady water, while guanacos can roam farther into dry country, and South American fur seals and sea lions gather on the coast.

  5253511196

• 5. Mars on Earth

  ›

  About 100 km south of Antofagasta, at an average elevation of 3000 m, the soil has been compared to that of Mars. Its otherworldly look led the producers of the 2004 television series Space Odyssey: Voyage to the Planets to film Mars scenes there.

  The scientific link is more serious. In 2003, a team of researchers published a report on an experiment that repeated the life-detection tests carried out by the Viking 1 and Viking 2 landers. In soil from the Yungay region, they could detect no signs of life. The same tests also missed signs of life that were present in samples from the Antarctic dry valleys and other Mars-like places. NASA uses the region to test instruments for future Mars missions. In 2014, researchers reported a still drier site called María Elena South, a better match for Martian conditions than Yungay.

  Chemistry adds another connection. In 2008, the Phoenix Mars Lander detected perchlorates at the same site where water was first found on Mars. Perchlorates also occur in the Atacama, and the nitrate deposits tied to them have contained organic material. That has led to speculation that perchlorates on Mars do not rule out signs of life. The desert also hosts the NASA-funded Earth-Mars Cave Detection Program.

  On the 21st of February 2023, scientists reported a dark microbiome of unfamiliar microorganisms in the Atacama. In December 2023, they described a newly discovered area in the Puna de Atacama, which may resemble Earth in the Archean eon, when the first life forms appeared. It could also resemble hospitable conditions on early Mars.

  1935403837

• 6. Salt, Silver and Nitrate

  ›

  Around 7000 BCE, the Chinchorro culture began to develop along the Atacama coast, and it lasted until 1500 BCE. These were settled fishermen whose presence stretches from Ilo, in southern Peru, to Antofagasta in northern Chile. Fresh water on the coast made settlement possible. They became famous for detailed mummification and funerary practices.

  Inland, the Atacameño people lived before the Inca and the Spanish arrived, and they were different from the Aymara to the north and the Diaguita to the south. They built fortified towns called pucarás, one of which stands a few kilometers from San Pedro de Atacama. That town sits at about 2400 m, and the Spanish built its church in 1577. During the Inca Empire, the oasis of Pica served as a stopover between the coast and the Altiplano. Inca authorities also moved the Moyos Moyos, whose tentative homeland is the Tarija Valley, into the desert as part of a population transfer.

  Water at the oases came through underground channels called puquios. Around 1900 they were spread through valleys and oases, including Azapa, Sibaya, La Calera, Pica-Matilla and Puquio de Núñez. In 1918, the geologist Juan Brüggen noted 23 shafts in the Pica oasis, though economic and social change has since led to their abandonment.

  Under Spain, coastal cities rose in the 16th, 17th and 18th centuries as shipping ports for silver from Potosí and other mining centers. At the end of the 18th century, Carlos IV set the southern border of the Viceroyalty of Peru at the port of Nuestra Señora del Paposo.

  The 19th century changed everything. Bolivia, Chile and Peru all claimed pieces of the desert, and the discovery of sodium nitrate, together with Chilean expansion plans, turned it into a conflict zone. The result was the War of the Pacific, after which Chile annexed most of the desert. Guano and saltpeter booms drew a flood of migrants, mostly from central Chile.

  About 170 nitrate mining towns now lie abandoned across the desert, nearly all of them shut down after German chemists invented synthetic nitrate in the first decade of the 20th century. Chacabuco, Humberstone, Santa Laura, Pedro de Valdivia, Puelma, María Elena and Oficina Anita are among them. Natural nitrate, the largest supply on Earth, was still mined on a large scale until the early 1940s. As the industry declined, the largely male population became a growing problem for the Chilean state, and miners and companies clashed in protests across the region.

  The ground still holds wealth. Copper, gold, silver, iron, boron, lithium and potassium salts are all found here, and bischofite is extracted at the Salar de Atacama. The desert is the largest source of iodine-bearing minerals, with some areas holding iodine hundreds of times above the average in Earth's crust. Companies such as Codelco, Lomas Bayas, Mantos Blancos and Soquimich work these deposits.

  5556646265

• 7. The Clearest Sky

  ›

  More than 200 cloudless nights a year fall over the Atacama, and the dry air, high altitude and absence of light pollution and radio interference make it one of the best observing sites anywhere. Through a telescope, hundreds of thousands of stars can be seen. The European Southern Observatory runs three major sites here: La Silla, Paranal, which includes the Very Large Telescope, and Llano de Chajnantor, home of the ALMA radio observatory.

  ALMA was built by European countries, Japan, the United States, Canada and Chile, and it officially opened on the 3rd of October 2011. Radio projects such as the CBI, the ASTE and the ACT had already operated in the Chajnantor area since 1999. On the 26th of April 2010, the ESO council chose Cerro Armazones as a fourth site, for the Extremely Large Telescope, and construction work there began in June 2014. Farther south, the Carnegie Institution for Science operates the Las Campanas Observatory with several telescopes.

  7475777672

• 8. Sand, Sport and Strain

  ›

  The Dakar Rally, organized by the Amaury Sport Organisation, ran through the Atacama in 2009, 2010-2011 and 2012, using dunes on the outskirts of Copiapó. The 2013 edition, a 15-day rally, started on the 5th of January in Lima, Peru, crossed Chile and Argentina, and finished in Santiago. Visitors also ride the dunes on sandboards. A week-long foot race called the Atacama Crossing takes runners across the desert's different landscapes, and the Volcano Marathon is held near the Lascar volcano.

  In November 2012, eighteen solar-powered cars were shown in front of the La Moneda presidential palace in Santiago. From the 15th to the 19th of November they raced 1300 km through the desert.

  Tourism ranks among the top three attractions in Chile, and most visitors stay in San Pedro de Atacama. About 80 geysers lie in a valley some 80 km from the town, near Chiu Chiu. The ESO hotel, built specially for the purpose, is reserved for astronomers and scientists.

  Not every new arrival is welcome. The desert receives an estimated 39,000 tonnes of illegally dumped used clothing each year, according to the highest available estimates. Because of the dry conditions, the clothes do not decompose at the usual rate, and fires have exposed nearby residents to air pollution.

  Since 2024, the Spanish company Grenergy has been building Oasis de Atacama, a solar-powered storage battery. It combines about 2 GW of solar capacity with 11 GWh of storage, and an agreement with BYD covers 3 GWh of the storage systems.

  8283706989