Privileged Location

ALMA’s administrative offices are located in Santiago, Chile’s capital city. Astronomers, administrative and technical professionals work here to support the rest of the team at the observatory in northern Chile. One of the tasks the Santiago astronomers are responsible for is processing the data collected by the telescope in order to provide their colleagues with an interpretable data package for their research, resulting from their observation time at ALMA.

Its climatological and geographical characteristics have made the northern Chilean region a global leader in astronomy.

In the last decades, Chile has become a leading country in the field of astronomy. The climatological and geographic characteristics of the Atacama Desert in northern Chile, which ensure the clarity of its skies, added to the high Andean mountain range provide unique conditions on Earth. In addition to this, it has the privileged southern sky that allows to observe many important objects at astronomical level, such as the center of the Milky Way and the Magellanic Clouds, among others. Many international cooperative efforts have taken place in this territory, which is home to the majority of the most powerful observatories. Such is the transparency of its skies that the resolution of images obtained at ALMA has exceeded that of the Hubble Space Telescope.

Array Operations Site (AOS)

Map showing the location of the Operation Support Facility (OSF). Most of the observatory activities are performed at the OSF, located at some 30 kilometers of San Pedro de Atacama, and at 2,900 meters above sea level. It’s a compulsory stop on the route to Chajnantor, where the ALMA antennas are located.

Atacama Desert

ALMA observes light that is invisible to the naked eye, a light that emanates naturally from the Universe in long waves, a portion of the electromagnetic spectrum that lets us explore the “cold Universe”. This is not picked up by optic telescopes and is fundamental if we want to know how stars and planets are formed.

The water vapor in the atmosphere absorbs these waves, hindering their collection on Earth. This is why the ALMA antennas were located in one of the most arid areas in the world: the Atacama Desert. Due to its dryness, high altitude, scant clouds and scarce radio interference and light pollution from cities, this desert is one of the best places on Earth for astronomic observation.

Located approximately 30° south latitude, this desert is enclosed by two mountain ranges: the Andes mountains to the east and the Domeyko mountain range to the west; covering an area of 181,300 square km. Over 20 million years old, this territory includes salt basins, sand and lava flows, and the driest sector is located south of the Loa River, west of the Domeyko mountain range and close to the municipality of San Pedro de Atacama and the town of Toconao, where ALMA is located. The cold Humbolt current and the Pacific anticyclone are fundamental in maintaining this dry climate.

Large volcanoes, such as Licancabur, Acamarachi, Aguas Calientes and Láscar, dominate the landscape. Láscar is one of the most active volcanoes in Chile. These volcanoes are all situated along the eastern side of the Atacama Salt Flat, forming a line of north-south trending volcanoes.

The soils in this site, interestingly enough, can be likened to those on Mars due to their dryness. This led NASA to test its robot, Zoe, in this area before sending it off to the red planet. In 2003, a team of researchers published a report in the Science journal entitled “Mars-like soils in the Atacama Desert, Chile, and the dry limit of microbial life,” which duplicated the tests used on Mars by the landing probes, Viking 1 and Viking 2, to detect life. They couldn’t find any evidence in the Atacama desert soil, which is perhaps the only region on Earth with this characteristic.

Chajnantor Plateau

After searching the world over for the perfect place to receive millimetric and submillimetric waves, scientists identified a plateau where the conditions were unmatched: Chajnantor. In the middle of the Atacama desert in northern Chile, they found a vast expanse of plains at five thousand meters above sea level, where the climate’s extreme aridity presented the perfect conditions for receiving cosmic waves. At a high altitude, with a broad surface and favorable climate, ALMA had found its home.

However, they were not the first to discover this key site. Proof of this lies in the origin of the word Chajnantor, meaning “launch site” in the Kunza language of the Atacameños, or Likan Antai, the original indigenous people who have been coming to this site to scrutinize the heavens for centuries.

Unlike the occidental worldview, concentrated on observing shiny objects in the sky, the Andean worldview distinguishes constellations, observing dark sectors of the night sky, the same dark Universe that ALMA is currently investigating.

“Our ancestors were able to read the signs in the sky to survive the vagaries of climate and enjoy the bounty of Mother Earth (…) now we know that our ancestors are true observers of the heavens and the first true astronomers in Atacama,” indicates an Atacameño descendent in the extract of the book, “The Universe of Our Elders,” supported by ALMA.

Likan Antai Territory

All of ALMA’s operations are carried out in territory provided in a concession by the government of Chile in the Atacama desert, one of the driest places on Earth. Although the landscape is stark, there are communities that have lived here for a long time. The Atacameño people, known as Likan Antai, have raised llamas and alpacas here for hundreds of years, and still maintain this tradition, along with weaving and crafting of jewelry. They are currently the third-largest indigenous community in Chile.

ALMA restored the Estancia Barrio ranch (see photo), where brothers Pedro and Viviano Cruz lived until the 1960s. Depending on the time of year and availability of water, the Cruz brothers moved their animals over almost 20 ranches among the gorges, in order to feed them.


Estancia Barrio

Today the Estancia Barrio ranch has been converted into a museum on the road between the OSF and Chajnantor, in memory of its original inhabitants and to preserve their customs.

Flora and Fauna

Despite its similarity with a Martian landscape, the Atacama Desert is home to native flora and fauna, which over centuries have developed techniques to adapt to the rugged living conditions. ALMA workers frequently spot vicuñas, vizcachas, flamingos, foxes, the cardon cactus, rica-rica and llareta, animals and plants that inhabit this incredible landscape.