FAST FACTS
Where is it? Etosha Pan, Namibia (-18.5946865, 16.04684972)
What is in the picture? A series of colorful, ephemeral lakes that appeared after a flood event
Who took the picture? An unnamed astronaut aboard the International Space Station (ISS)
When was it taken? 30 December 2011
This exciting astronaut image shows the contrasting colors of five ephemeral lakes that appeared around the edges of a giant salt pan after a major flood event in southwest Africa.
The kaleidoscopic scene took place in the northwest corner of the Etosha Pan — Africa’s largest salt flat, or mineral pan, covering about 1,800 square miles (4,730 square kilometers) in northern Namibia. The name Etosha roughly translates to “Great White Place” in an indigenous Namibian language, and the ghostly expanse lies about 400 kilometers from the country’s capital, Windhoek.
The satellite image shows a meandering pair of ephemeral rivers flowing into the Etosha Pan: the Ekuma River (left) and the Oshigambo River (right). These winding waterways are surrounded by about a dozen bowl-like depressions that occasionally fill with water when rivers occasionally flood their banks.
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When the photo was taken, both rivers had recently flooded due to heavy rains in the region, causing about half of these pale depressions to be filled with water. The rest of the lakes remained empty and have the same pale hue as the rest of the Etosha Pan.
The contrasting colors of the newly filled lakes — which include yellow, green, brown, red and pink — are likely the result of different species of algae that flourished in their shallow waters, according to NASA’s Earth Observatory. (For scale, Green Lake is around 4 miles (6.5 km) long at its widest point.)
The Etosha Pan probably formed about 10 million years ago and has been a freshwater lake for most of that time. But about 16,000 years ago, toward the end of the last ice age, tectonic activity diverted one of the major rivers that flowed into the lake, causing it to dry up.
As the water slowly evaporated, it left a thick layer of minerals covering the lake. Most of the pan’s surface is covered by honeycomb-like hexagonal structures that are common among salt flats around the globe.
During flood events, a thin layer of water can briefly remain in the pan, transforming it back into a shallow lake. However, this rarely happens, even when the rivers flood.
The last time a majority of the pan flooded was in 2006, which it was captured from space of ISS astronauts.
Wildlife haven
Despite Etosha Pan’s extreme dryness and salinity, which make it largely inhospitable to life, the area around the ancient lake is covered in rich grasslands and forests.
This diverse ecosystem is protected as part of Etosha National Park, which covers 8,900 square miles (23,000 square kilometers), and is home to a variety of animals, including lions, giraffeszebras, hyenas, impalas, elephantsrhinoceros, springbok, wildebeest and ostrichesaccording to iNaturalist.
The salt flats themselves are also an important breeding site for flamingos, and up to 1 million of the pink birds congregate there at a time, according to Etosha National Park website.
If you look closely at the astronaut image, you can see the park’s northern fence running across the image from left to right – directly above the green lake and dividing the red and pink lakes. This 10-foot-tall (3-meter) barrier stops the park’s animals from wandering outside the forests where they could be targeted by poachers, according to the Earth Observatory.
A satellite image from 2023 shows three tightly clustered lakes in Ethiopia’s Great Rift Valley. They have distinctly different hues thanks to a combination of biological and geological factors.
A 2014 satellite image of the Sivash region shows the kaleidoscopic colors of a series of shallow, hypersaline lagoons—each filled with a different type of algae.
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