Sandstorm Over the Sahara

A sandstorm over the Sahara desert in Africa seen by ESA astronaut Alexander Gerst from the International Space Station.

Photo credit: ESA/NASA

Sahara Irrigation

Amazing colors of the Sahara desert are captured in this photograph taken from onboard the International Space Station. ESA astronaut Alexander Gerst shared this image on Twitter with the comment: "Irrigation in the Sahara Desert looks like a challenging task from up here...".

Alexander Gerst is currently a member of the resident International Space Station Expedition 40 crew. He is spending five and a half months living and working on the ISS for his Blue Dot mission.

Photo credit: ESA/NASA

Richat Structure, Mauritania

A giant, geological wonder in the Sahara Desert of Mauritania is pictured in this satellite image.

The 40 km-diameter circular Richat structure is one of the geological features that is easier to observe from space than from down on the ground, and has been a familiar landmark to astronauts since the earliest missions.

Once thought to be the result of a meteor impact, researchers now believe it was caused by a large dome of molten rock uplifting and, once at the surface, being shaped by wind and water into what we see today. Concentric bands of resistant quartzite rocks form ridges, with valleys of less-resistant rock between them.

The dark area on the left is part of the Adrar plateau of sedimentary rock standing some 200 m above the surrounding desert sands. A large area covered by sand dunes – called an erg – can be seen in the lower-right part of the image, and sand is encroaching into the structure’s southern side.

Zooming in on the southern side of the bullseye, we can see individual trees and bushes as tiny dots. These follow a river-like structure that appears to have been dry when this image was acquired, a few weeks after the rainy season. Some areas to the south and east of the Richat appear to be covered with temporary lakes, which are dry for most of the year.

This image, also featured on the Earth from Space video program, was acquired on 23 November 2010 by the Advanced Visible and Near Infrared Radiometer on Japan’s ALOS satellite.

Image credit: JAXA/ESA

Aorounga Crater, Chad

This image from Japan’s ALOS satellite shows the Aorounga Crater in northern Chad.

The crater is just south of the Tibesti Mountains, a range of inactive – with some potentially active – volcanoes in the central Sahara desert.

Measuring about 12 km across, the crater was created by a meteorite impact about 340 million years ago.

Clearly visible is the dark, central peak, caused by material splashing up after the impact, similar to how water bounces back up when a stone is thrown in. This peak is surrounded by a low, sand-filled ring, which is surrounded by another ring of rock from when the material was thrown outwards. A distinctive low, sand-filled trough circles the others – the outer edges of the initial impact.

The linear rock ridges that run diagonally across this image are ‘yardangs’ and are formed by wind erosion. Here, we can clearly see how the wind blows from northeast to southwest. Sand dunes form in the wind-cut valleys between the rock ridges of the yardangs.

Japan’s Advanced Land Observation Satellite captured this image on 3 November 2010. ALOS was supported as a Third Party Mission, which means that ESA used its multimission ground systems to acquire, process, distribute and archive data from the satellite to its user community.

This image is featured on the Earth from Space video program.

Photo credit: JAXA/ESA

Libya's Al-Jawf Oasis

Deep in the Sahara Desert, the Al Jawf oasis in southeastern Libya is pictured in this image from Japan’s ALOS satellite. The city can be seen in in the upper left corner, while large, irrigated agricultural plots appear like Braille across the image. Between the city and the plots we can see the two parallel runways of the Kufra Airport. The agricultural plots reach up to a kilometer in diameter. Their circular shapes were created by a central-pivot irrigation system, where a long water pipe rotates around a well at the center of each plot. Since the area receives virtually no rainfall, fossil water is pumped from deep underground for irrigation.

Japan’s Advanced Land Observing Satellite (ALOS) captured this image on 24 January 2011 with its Advanced Visible and Near Infrared Radiometer type-2, which charts land cover and vegetation in the visible and near-infrared spectral bands at a resolution of 10 m. ESA supports ALOS as a Third Party Mission, which means ESA uses its multi-mission ground systems to acquire, process, distribute and archive data from the satellite to its user community.

This image is featured on the Earth from Space video program.

Photo credit: JAXA, ESA

Star Dunes in the Algerian Sahara

Radially symmetrical, star dunes are pyramidal sand mounds with slipfaces on three or more arms that radiate from the high center of the mound. They tend to accumulate in areas with multidirectional wind regimes. Star dunes grow upward rather than laterally. They dominate the Grand Erg Oriental of the Algerian Sahara, as depicted in this image acquired October 27, 2012. It covers an area of 37 x 43 km, and is located at 29.8 degrees north latitude, 7.9 degrees east longitude.

Photo credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team

Algerian Sands

This image shows the sandy and rocky terrain of the Sahara desert in western Algeria. With the Mediterranean Sea almost 500 km away, the closest town to the area pictured here is Taghit in the Algerian province of Béchar.

The commercial Ikonos-2 satellite acquired this image on 23 April 2008 at a spatial resolution of 4 m.

Photo credit: EUSI

Morocco and Algeria

This Envisat image, acquired on 5 December 2011 by the MERIS instrument, shows part of central Morocco from the Atlantic Ocean to the west, over the Atlas mountains and into arid parts of Algeria further inland. The snow-capped High Atlas mountain range divides Morocco from the Sahara desert’s climatic influences in Algeria. The Sahara is constantly expanding southward, rendering large areas of land barren. One of the many benefits of Earth observation satellites is the possibility to monitor changes like desertification, or the degradation of land, caused by human activities or climate change.

Photo credit: ESA