The original caption from NASA:
This vertically exaggerated view shows scalloped depressions in Mars’ Utopia Planitia region, one of the area’s distinctive textures that prompted researchers to check for underground ice, using ground-penetrating radar aboard NASA’s Mars Reconnaissance Orbiter.
More than 600 overhead passes with the spacecraft’s Shallow Radar (SHARAD) instrument provided data for determining that about as much water as the volume of Lake Superior lies in a thick layer beneath a portion of Utopia Planitia.
These scalloped depressions on the surface are typically about 100 to 200 yards or meters wide. The foreground of this view covers ground about one mile (1.8 kilometers) across. The perspective view is based on a three-dimensional terrain model derived from a stereo pair of observations by the High Resolution Imaging Science Experiment (HiRISE) camera on the Mars Reconnaissance Orbiter. One was taken on Dec. 25, 2006, the other on Feb. 2, 2007.
The vertical dimension is exaggerated fivefold in proportion to the horizontal dimensions, to make texture more apparent in what is a rather flat plain.
Similar scalloped depressions are found in portions of the Canadian Arctic, where they are indicative of ground ice.
Diagonal striping on this map of a portion of the Utopia Planitia region on Mars indicates the area where a large subsurface deposit rich in water ice was assessed using the Shallow Radar (SHARAD) instrument on NASA’s Mars Reconnaissance Orbiter.
The scale bar at lower right indicates 140 kilometers (76 miles). The violet vertical bars show depth to the bottom of the ice-rich deposit, as estimated from SHARAD passes overhead. Darkest violet indicates a depth of about 550 feet (about 170 meters). Palest violet indicates a depth of about 33 feet (10 meters). The value of 2.8 plus-or-minus 0.8 in the upper right corner denotes the dielectric constant, a property related to radar reflectivity. The value of 14,300 cubic kilometers is an estimate of the volume of water in the deposit. — NASA
Images: NASA/JPL-Caltech/Univ. of Rome/ASI/PSI/Univ. of Arizona