Pits, Cracks, and Polygons in Western Utopia Planitia (context image) - Elab. Lunexit

Utopia Planitia is part of the Great Northern Lowlands of Mars, where there may have been an ancient ocean.
The pits, cracks and polygons in Utopia have been interpreted as due to some combination of temperature variations in ice-rich ground, sublimation of ground ice, and collapse into subsurface voids.

This HiRISE image reveals many new details, including an abundance of boulders about 1 mt in diameter over the entire region (see the extr-detail mgnf).
The infrared color of HiRISE reveals two types of materials: the brighter and yellowish areas are probably dusty and the darker and bluer areas are probably coarser particles--sand and rocks.