Viking 1 Orbiter image showing patterned ground in the northern lowland plains of Mars. The individual polygons bounded by the fractures can be up to 20 km across, much larger than the 100 m sizes found in the nearest terrestrial analogue, ice wedging in periglacial regions. The image is 85 km across and north is at 1:30.
(Viking Orbiter 32A18)
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