This image shows the western rim of a well-preserved 8.5-kilometer (about 5 miles) diameter impact crater.
The wall features a slumped terrace that extends all the way around the crater diameter (the adjacent image show the rest of the terrace). This slumped terrace, a result of the crater formation process, gives the crater a concentric ringed appearance.
Terraces are an expected feature in Martian craters of this size or larger, as the material strength of the surface is overcome by the force of all-of-the-sudden-missing mass. Blocks of rock slump down the steep crater walls and slide inward (by contrast, terraces in smaller craters are often the product of an impact of an object into a surface with layers of differing material strength).
Photo credit: NASA/JPL/University of Arizona
Note: This impact crater is located to the northwest of Alba Mons and its lava flows.
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