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Breached Impact Crater in Memnonia PSP0033591650
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Breached Impact Crater in Memnonia PSP_003359_1650

July 14, 2007
PSP_003359_1650 shows the south rim of an impact crater in Memnonia. This crater is breached by valleys on its north and south ends (not seen here) and has terraces. Terraces are different levels up and down a crater wall that appear stair-like. The valleys and terraces suggest that this crater might have had a lake at one point in its history.

This HiRISE image shows a heavily cratered surface. The crater floor (top of the scene) is covered in craters and dunes indicating that its surface has been exposed for a long period of time. The crater wall (approximately center) also has abundant craters. Many of the craters are very small and found in clusters (for an example, look just down and below the largest crater near the center of the image). These are likely secondary craters--craters that are formed by ejecta that are a result of a separate, larger impact event.

What is particularly interesting about these craters is that many of them are surrounded by bright material (see subimage). When a crater forms, an object hits the surface and throws out a lot of underlying material. It is possible that the bright material around the craters represents material that was excavated during the impact events. The bright material looks raised around several of the craters, suggesting that it is cemented and therefore more resistant to erosion by wind. The material could be bright because of its particle sizes or composition.