Salar de Uyuni from the ISS (annotated version)

Salar de Uyuni from the ISS (annotated version)

While orbiting over South America, an astronaut on the International Space Station shot this photograph of the Atacama Desert and the numerous salt flats in the Andes Mountains along the border of Chile and Bolivia. The centerpiece is the Salar de Uyuni, the largest salt flat on Earth. It regularly captures the attention of astronauts due to its high contrast against the brown landscape.

Salar de Uyuni and its smaller neighbor, Salar de Coipasa, have darker tones along their edges in this image. These dried lake beds are typically bright white in color, but rainfall can bring an influx of dark volcanic sediments. The region experienced rainfall in early February 2019, which caused temporary discoloration of the salars. By the time this image was taken in March 2019, the flats had started to shift back to their lighter colors.

Nearby, the much smaller Laguna Colorada displays bright hues thanks to algae that thrive in the salty water. To the west and northwest of the lake, some of the white dots are snow-capped volcanoes and mountains.

The salars receive less than 200 millimeters of rainfall per year. In contrast, the cloud-covered parts of Bolivia (north of the salars) see more than 1,750 mm of rain annually. The Andes Mountains create a rain shadow effect along the coast of northern Chile and western Bolivia, as air masses carrying moisture from the east drop most of their water before cooling and moving up over the mountains.

Along the coast, the Atacama Desert is one of the driest places on Earth, sometimes going years without rainfall. NASA uses the Atacama Desert to test rovers and other instruments because the area is a good analogue for future astrobiological exploration of Mars.

Image source: NASA Earth Observatory webpage

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