Ground cemented by ice covers the high latitudes of Mars, much as it does in Earth’s cold climates. A common landform that occurs in icy terrain are polygons.
Polygonal patterns form by winter cooling and contraction cracking of the frozen ground. Over time these thin cracks develop and coalesce into a honeycomb network, with a few meters spacing between neighboring cracks. Shallow troughs mark the locations of the underground cracks, which are clearly visible from orbit. [More at link]