FAST FACTS
Where is it? Taklamakan Desert, China (38.459991514, 80.87050739)
What is in the picture? A river and a mountain range forming a giant Y shape
Which satellite took the picture? Landsat 9
When was it taken? 11 September 2025
This striking satellite image shows a massive letter Y lurking in the heart of a recently transformed Chinese desert. The unusual shape consists of a rocky ridge and a winding, gem-filled river and is also home to an important 7th-century fort.
The desert was previously considered a “biological void” – meaning it was almost completely devoid of life – due to its high temperatures and dryness. However, an ecological engineering project is known as Great green wall hair planted more than 66 billion trees along the desert’s northern edge since 1974, which has turned it into a carbon sink which soaks up large amounts of carbon dioxide, recent research revealed.
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The Y-shape consists of two parts: the Hotan River, which stretches about 290 kilometers across the desert from south to north; and Marzatagh, a “wall-like” ridge that rises about 600 feet (180 meters) above the surrounding sand and extends up to 90 miles (145 km) to the northwest, according to NASA’s Earth Observatory.
The Hotan River (sometimes called the Khotan River) is fed by glacial meltwater from the Kunlun Mountains south of Taklamakan and looks green due to vegetation growing between its braided streams. The water is rich in both white and green nephrite, which are precious types of jade.
Marztagh is divided into seams of reddish iron-rich rocks and paler sandstone, giving it the name Hongbaishan, which means “red-white mountain” in Chinese. It also acts as a natural barrier to sand being blown against the rocky wall, creating a sea of rippling, crescent-shaped “barchan” dunes along its northern edge.
The confluence of drinking water, valuable gems and shelter from the elements made this place an important stop on the Silk Road – a massive network of trade routes running from east to west across Asia from the second century to the fifteenth century.
The point where the two features meet is home to the crumbling remains of a military fort, probably dating to the eighth century.
Crumble fast
The fortress, called Mazar Taghwas built on a hill at the intersection of the Y-shape of the Tibetan Empire, which existed between 618 and 842 AD. and covered most of the Tibetan Plateau, including parts of present-day China, India, and Afghanistan.
The site was first excavated in 1907 by the Hungarian-British archaeologist Aurel Stein, who uncovered more than 1,500 document fragments, transcribed on both wood and paper, according to The International Dunhuang Program. These texts were written in several languages - including Khotanese, Uyghur and Sogdian – and document the soldiers’ experiences.
Other artefacts – including arrows, scabbards, shoes, dice, a comb and a pen – were also found at the site and are currently stored at the British Museum. However, the most impressive find was undoubtedly one portrait of a “begging monk” painted on a wooden board, probably by a soldier. The monk was probably on a pilgrimage to an old Buddhist shrine that was built on the same hill.
Today, the hill is also home to an Islamic shrine.
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