The driest non-polar desert is also a fog-fed observatory
Chile's Atacama is the driest non-polar desert and the largest fog desert on Earth, a 1,600-kilometre strip wedged between the Andes and the Coast Range. Some weather stations there have never recorded rain, peaks above 6,000 metres stand free of glaciers, and its dark, dry skies host observatories such as ALMA.
The desert covers about 105,000 square kilometres, or 128,000 counting the barren lower Andean slopes. Its dryness comes from a two-sided rain shadow, with the Andes and the Chilean Coast Range blocking moisture from both oceans, reinforced by the cold Humboldt Current and the South Pacific anticyclone. Rainfall averages about 15 millimetres a year and some spots get only 1 to 3; near the abandoned mining town of Yungay, often called the driest place on Earth, the University of Antofagasta runs a research station.
It may be the oldest desert on the planet, hyperarid since at least the Middle Miocene, after a proto-Humboldt current formed when the Tasmania–Antarctic passage opened about 33 million years ago. Yet a capybara fossil roughly 8.8 million years old, found with palm phytoliths, points to rivers and wetlands in the past. British researchers have suggested certain riverbeds there last carried water 120,000 years ago, though coastal fog called camanchaca sustains life in places. Rare storms can kill: mudflows in 1991 killed 91 people around Antofagasta, and 2015 floods more than 100.
Soil south of Antofagasta has been likened to that of Mars. In 2003 researchers repeating the Viking landers' life-detection tests near Yungay found no sign of life, and NASA now tries out Mars instruments there; perchlorates like those Phoenix detected on Mars in 2008 occur here too. Even so, a dark microbiome of unfamiliar microbes was reported in 2023, and over 500 plant species grow in the desert, including the endemic tamarugo and the cushion-shaped llareta, many of which exceed 3,000 years in age.
The Chinchorro culture settled the coast by at least 7000 BCE, followed by the Atacameño and, under the Inca, Aymara communities. Spanish colonial ports shipped silver, and the Pampa del Tamarugal woodland was felled for mining fuel in the eighteenth and nineteenth centuries. Rich sodium nitrate deposits later set Chile, Bolivia and Peru against one another in the War of the Pacific.
Source: Atacama Desert
