The Atacama Desert (Spanish: Desierto de Atacama) is a desert plateau located on the Pacific coast of South America, in northern Chile. It extends over a strip of land 1,600 kilometres (1,000 mi) long west of the Andes Mountains, covering an area of 105,000 square kilometres (41,000 sq mi), increasing to 128,000 square kilometres (49,000 sq mi) if the arid lower slopes of the Andes are included. The Atacama Desert is the driest non-polar desert in the world, and the second driest overall, after certain specific spots within the McMurdo Dry Valleys. It is the only true desert that receives less precipitation than the polar deserts, and the largest haze desert in the world. The area has been used as a test site for a Mars mission simulation because of its similarity to the Martian environment.
The constant temperature inversion caused by the cold Pacific Ocean current flowing northward and the powerful Pacific Ocean cyclone contribute to the extreme dryness of the desert. The driest part of the Atacama Desert is located between two mountain ranges, the Andes and the Chilean Coastal Range, which are high enough to block the convection of moisture from the Pacific or Atlantic Oceans, creating a rain shadow effect on both sides. Milky Way
Because of its high altitude, almost no cloud cover, dry air, and the absence of light pollution and radio interference from populated cities and towns, this desert is one of the best places in the world to conduct astronomical observations. Hundreds of thousands of stars can be seen through a telescope, with the desert experiencing more than 200 clear nights each year. A number of telescopes have been installed to help astronomers from around the world study the universe. The Atacama Large Millimeter Array (ALMA) radio astronomy telescope was officially inaugurated on October 3, 2011, built by the European countries, Japan, the United States, Canada and Chile at the Llano de Chagnator Observatory. A number of radio astronomy projects, such as CBI, ASTE and ACT, among others, have been operating in the Chagnator area since 1999. On April 26, 2010, the ESO Council decided to build a fourth site, Cerro Armazones, to be home to the Extremely Large Telescope. Construction began on the ELT site in June 2014. The Carnegie Institution for Science operates the Las Campanas Observatory with several telescopes in the southern part of the desert. The European Southern Observatory operates three major observatories in the Atacama and is currently building a fourth:
