Scallops and Polygons in the Utopia Planitia Region (extra-detail mgnf - MULTISPECTRUM; credits: Lunexit)

Several cracks cut through the side of the scallops suggesting that they must be at least as deep as the scallops. The polygons may have been present previous to the erosion of the mantle.

The landforms we observe here most likely show that ice-rich permafrost is present or has been present geologically recently. At this latitude on Mars, the conditions of pressure and temperature allow water ice within the ground to sublime.
The disappearance of the ice component of the ground probably leads to the formation of the depressions, a process that may still be active today.