Some such signs can be seen to the lower right of the main image, in the dark blanket of ash. Here, we can see vaguely rounded pits with wavy edges. Known fittingly as ‘scalloped depressions’, these features are very common in this part of Mars, and indicate that the region is periglacial (on the fringes of glaciers or in cold-climate landscapes, undergoing cycles of freezing and thawing, typically featuring lots of buried ice).
Scalloped depressions form as ice below the surface melts or escapes to the air, causing the covering ground to become unstable and collapse. They don’t occur in isolation but rather merge to form larger areas, providing a perfect example of how Mars’s surface is constantly changing.
A labyrinth of fractures
It may not command our attention in the same way as the dark ash, but the left half of this two-toned scene is just as fascinating.
Far on the left lies a curious feature seen often across Utopia Planitia: a series of shadowy ditches around 20 km long and 2 km wide stretching out across the surface, meeting to form a giant shape (see close-up below).