This prominent circular feature in the Sahara Desert of Mauritania has attracted attentionsince the earliest space missions because it forms a conspicuous bull’s-eye in the otherwiserather featureless expanse of the Gres de ChinguettiPlateau in central Mauritania, northwest Africa. Described by some as looking like an outsized ammonitein the desert, the structure [which has a diameter of almost 50 kilometers (30 miles)]has become a landmark for space shuttle crews. Initially interpreted as a meteorite impact structurebecause of its high degree of circularity, it is now thought to be merely a symmetricaluplift (circular anticline) that has been laid bare by erosion. Paleozoic quartzites form theresistant beds outlining the structure. The reason for the high degree of circularity is notclear.
This true-color scene was acquired by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA’s Terra satellite, on March 11, 2002.
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Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC
