Chasma Boreale (2)

Different layers show very different degrees of roughness and pitting, although the texture within a layer is quite consistent. One of the layers even displays a texture of polygons 3 up to 10 mt across, normally associated with periglacial freeze-thaw processes on Earth. Layers of different texture, brightness, and appearance indicate differing physical properties, composition and exposure to surface environmental conditions at time of emplacement and/or erosion.
In this way, polar layers on Mars record a history of climate conditions as sequences of layers on Earth often do.