Martian Mystery: 'Inca City'
Pictured is the Martian anomaly known as "Inca City," the informal name given by Mariner 9 scientists in 1972 to a set of intersecting, rectilinear ridges that are located among the layered materials of the south polar region of Mars. Their origin has never been completely understood. The second image shows the mysterious ridges in close-up. More here.
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