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Several geomorphic features have been cited as evidence that there has been downward flow of ice-rich materials in higher latitudes on Mars. Some features are compelling, and no doubt such flow has occurred. Also cited is the type of multiridged intracrater deposit shown here, called concentric crater fill because the ridge pattern typically parallels the crater rim. It is possible that concentric crater fill is an eroded aeolian deposit similar to the polar laminated terrain and is not necessarily a flow deposit, particularly since such a flow would not likely retain internal layering as seen in this example. In any case, all the flow-formed landforms have had their uppermost surface sculpted by aeolian erosion; the point of contention is how significant aeolian processes have been in the formation of such deposits. Note that the scour related to the crater ejecta is overlain by the plains units (arrow in inset B). Location: Latitude 44.9°, Longitude 270°, in Utopia Planitia. Viking orbiter photograph 010B70, NGF rectilinear version, clear filter. The location and orientation of the inset labels are the same on both the main photograph and on the insets themselves. Upper inset 425B07, NGF orthographic version, minus-blue filter. Lower inset: 425B11, NGF orthographic version, minus-blue filter. Click here to view a high-resolution version of the image (2.27 MB)
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