NASA's Mars Global Surveyor shows valley floors in the middle latitudes of Mars, particularly in the 'fretted terrain' of northern Arabia Terra which have curious grooved and pitted surfaces.

Valley floors in the middle latitudes, particularly in the "fretted terrain" of northern Arabia Terra (shown here) have curious grooved and pitted surfaces. These features not glaciers and show very little evidence (if any) of flow. Their origin is unknown. MOC image from July 1998.

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