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puzzling feature on the surface of Mars that can be seen in Mariner 9 frame 4209-75 (pictured below). It is also located in the equatorial area (at longitude 186.4) and has been described as "unusual indentations with radial arms protruding from a central hub" caused (according to NASA scientists) by the melting and collapse of permafrost layers.
The design of the features, bringing to mind the structure of a modern airport with a circular hub from which the long structures housing the airplane gates radiate, can be better visualized when the photograph is reversed.