North Africa: Rings of Rock in The Sahara | International Space Station
In northeastern Africa, within the driest part of The Sahara, dark rocky outcrops rise above pale desert sands. Several of these formations, including Jabal Arkanū, display striking ring-shaped structures.
Jabal Arkanū (also spelled Arkenu) lies in southeastern Libya, near the border with Egypt. Several other massifs are clustered nearby, including Jabal Al Anaynat (or Uweinat), located about 20 kilometers (12 miles) to the southeast. Roughly 90 kilometers to the west are the similarly named Arkenu structures. These circular features were once thought to have formed by meteorite impacts, but later fieldwork suggested they resulted from terrestrial geological processes.
Arkanū’s ring-shaped structures also have an earthly origin. They are thought to have formed as magma rose toward the surface and intruded into the surrounding rock. Repeated intrusion events produced a series of overlapping rings, their centers roughly aligned toward the southwest. The resulting ring complex—composed of igneous basalt and granite—is bordered to the north by a hat-shaped formation made of sandstone, limestone, and quartz layers.
This photograph, taken by an astronaut aboard the International Space Station on September 13, 2025, shows the massif casting long shadows across the desert. The ridges stand nearly 1,400 meters above sea level, or about 800 meters above the surrounding sandy plains. Notice several outwash fans of boulders, gravel, and sand spreading from the mountain’s base toward the bordering longitudinal dunes.
Two wadis, or typically dry riverbeds, wind through the structure. However, water is scarce in this part of The Sahara. Past research using data from NASA and the Japan Aerospace Exploration Agency's now-completed Tropical Rainfall Measuring Mission (TRMM) indicated that southeastern Libya, along with adjacent regions of Egypt and northern Sudan, receives only about 1 to 5 millimeters of rain per year. Slightly higher accumulations, around 5 to 10 millimeters per year, occur near Jabal Arkanū and neighboring massifs, suggesting a modest orographic effect from the mountains.
This is an astronaut photograph, taken by a member of the Expedition 73 crew. It was taken with a Nikon Z9 digital camera using a focal length of 800 millimeters.
The Sahara is a desert spanning across North Africa. With an area of 9,200,000 square kilometres (3,600,000 sq mi), it is the largest hot desert in the world and the third-largest desert overall, smaller only than the deserts of Antarctica and the northern Arctic.
The name "Sahara" is derived from Arabic: صَحَارَى, romanized: ṣaḥārā /sˤaħaːraː/, a broken plural form of ṣaḥrā' (صَحْرَاء /sˤaħraːʔ/), meaning "desert".
The desert covers much of North Africa, excluding the fertile region on the Mediterranean Sea coast, the Atlas Mountains of the Maghreb, and the Nile Valley in Egypt and the Sudan.
It stretches from the Red Sea in the east and the Mediterranean in the north to the Atlantic Ocean in the west, where the landscape gradually changes from desert to coastal plains. To the south it is bounded by the Sahel, a belt of semi-arid tropical savanna around the Niger River valley and the Sudan region of sub-Saharan Africa. The Sahara can be divided into several regions, including the western Sahara, the central Ahaggar Mountains, the Tibesti Mountains, the Aïr Mountains, the Ténéré desert, and the Libyan Desert.
Image Date: Sept. 13, 2025
Release Date: Nov. 28, 2025
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