QUICK FACTS
Where is it? Erg Chebbi, Morocco [31.07988204, -3.986015555]
What’s in the photo? A group of large “star dunes” near the edge of the Sahara desert
Who took the photo? An unnamed astronaut on board the International Space Station
When was it taken? Dec. 21, 2023
This intriguing astronaut photo shows around a dozen giant “star dunes” as they slowly dance across a sandy field near the edge of the Sahara desert. The rare dunes, which are often confused with human-made pyramids, are likely several centuries old, recent research has revealed.
The unusual structures are located in Erg Chebbi. This field of open, windswept sand — or erg — covers around 65 square miles (170 square kilometers) in southwest Morocco along the northwestern edge of the Sahara. The erg is surrounded by flat lowlands but contains some of the tallest dunes in the Sahara, making it stand out like a mountain range when viewed from afar.
The town of Merzouga is also visible in the bottom right of the image. This settlement is built on top of a large aquifer, or underground reservoir, which allows palm groves to flourish alongside the desolate landscape and draws in tourists who are looking to explore the erg’s sandy peaks.
A star dune is a type of sand dune that has at least three ridges coming from a central peak, which gives it a star-like shape when viewed from above, according to NASA’s Earth Observatory. But when they’re viewed from the side, their multiple smooth slopes, known as “slip faces,” can make the star dunes look very similar to pyramids from ground level.
These dunes, which can grow to be over 300 feet (90 meters) tall, form only in locations where wind directions change constantly, which allows their different slopes to form, according to the National Park Service. As a result, they move by just a couple of inches every year in the direction of the strongest prevailing wind. That’s a lot slower than some other wandering dunes, which can travel up to 1,000 feet (300 m) annually when blown in a single direction.
Related: See all the best images of Earth from space
The largest star dune in Erg Chebbi, Lala Lallia, is 330 feet (100 m) tall and is located slightly to the north (left) of the dunes in the satellite image. In March 2024, researchers revealed that this dune is around 900 years old, which is much younger than previous estimates had suggested.
The same study also revealed that some of the sand buried at the base of this dune is up to 13,000 years old. These grains predate an 8,000-year period of climatic change that occurred after the end of the last ice age. During this time, the Sahara was temporarily transformed into a swampy environment covered in vegetation — a shift that ended only around 4,000 years ago, researchers wrote at the time.
On Earth, star dunes are also found in China, Namibia, Algeria, Saudi Arabia and several U.S. states, including California and Colorado. But very similar structures can be found on Mars, according to NASA.
