Ancient Layered Rocks in Nili Fossae (edm - natural colors; credits: Lunexit)

Bright, fractured Bedrock is visible underlying Dunes or Ripples of Wind-Blown Sand.
The parallel, dark brown curves across the Bedrock Surface (underneath the Dunes) that can be seen in this edm frame, are the edges of successive rock layers.

These may appear dark because dark sand has become trapped at the edges of the layers. Successive layers in the bedrock are also exposed in the walls of degraded impact craters elsewhere in the ctx image.

The Layered Rocks here are billions of years old, and infrared spectra from the CRISM instrument have inferred that they contain minerals such as Clays and Carbonate that likely formed when liquid water chemically altered these rocks.
This evidence for past water activity, combined with the general flatness of this particular location, make it a good candidate Landing Site for future Mars Rover missions.