Southern rim of Isidis Planitia basin

This image, crossing the southern rim of the Isidis Planitia basin, displays the contrasting morphologies of the relatively rough highland terrain (in the lower portion of the image) and the relatively smooth materials of the basin (at top). Upon closer viewing, the basin materials display an extensive record of cratering, including a small cluster of craters just north and west of the two prominent craters in the upper part of the image. This cluster of craters may represent what are called 'secondary' craters, which are craters that form as a result of the ejection of debris from a nearby impact. Alternatively, these craters may have formed simultaneously by the impact of many pieces of a larger meteoroid that broke up upon entry into Mars' atmosphere. The large craters in the image are approximately 800 meters (~875 yards) in diameter. Also visible in the image are dark streaks on the east-facing side of the north-south trending ridge. These streaks are likely the result of debris movement down slope. A dark patch of material is visible at the left of the image; dark materials are typically mobile sands, and linear duneforms are apparent within the dark patch.