A linear depression, or trench, can be traced across the middle of the picture. The bottom of the trench is 10 to 15 cm lower than bordering lips. It is partly filled with sediment finer than on adjacent surfaces. The sediment apparently has been scalloped by the wind.
Larger rocks are relatively rare, and the few that are present are partly buried by finer sediment.
The trench seen here is part of a more extensive polygonal network that occurs near the Lander. The origin is uncertain but it is possible that the polygonal soil structure is the result of cyclic freezing and thawing of groundwater. Analogous structures form in periglacial regions on Earth. During spring, meltwater segregates in the soil and freezes to form an ice wedge. Expansion of permafrost during the summer causes an upward bulge in the vicinity of the ice wedge.