on the European Space Agency Web TV.

A giant, geological wonder in the Sahara Desert of Mauritania

is pictured in this satellite image.

Measuring 40 km in diameter the 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.

This image was acquired on 23 November 2010 by the Advanced Visible and Near Infrared

Radiometer on Japan's ALOS satellite. 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 can be seen in the lower-right part of the image,

and sand is encroaching on the structure's southern side.

Zooming in on the southern side of the bullseye, we can see individual trees and bushes appear

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 by temporary lakes, which

are dry for most of the year.

Well that wraps up this edition of Earth from Space.

Remember that we broadcasting online every Friday at ten o'clock Central European Summer Time

Watch us on our website or through the ESA App on your mobile device

From the ESA Web TV studios I'm Kelsey Brennan-Wessels