Hi I'm Kelsea Brennan-Wessels and welcome back to Earth from Space
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