Contact between Two Distinct Types of Bedrock Northwest of Hellas Planitia

In this image from NASA Mars Reconnaissance Orbiter is an old degraded crater that has undergone a complex history of burial and erosion. The image shows a surface with at least two types of exposed bedrock, one that is light-toned and one that is dark.

The overlying, rougher blueish-toned bedrock appears to have undergone the most extensive erosion, revealing the smoother, fractured yellowish-toned bedrock below. We see windblown (aeolian) bedforms across the image, possibly the culprit behind the erosive forces that have removed and uncovered the underlying yellowish-toned bedrock visible today.

http://photojournal.jpl.nasa.gov/catalog/PIA11705