Image Credit: NASA/JPL/ASU

Context image credit: NASA/JPL/MOLA
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Originating on the margin of Lunae Planum, the Kasei Vallis complex contains two main channels that run east-west across Tempe Terra and empty into Chryse Planitia.

The formation of Kasei Vallis is still being studied and several theories exist. It is thought that volcanic subsurfaceing heating in the Tharsis/Lunae Planum region resulted in a release of water, which carved the channels and produced the landforms seen within the channels. One theory is that this was a one-time catastropic event, another theory speculates that several flooding events occurred over a long time period. Others have proposed that some of the landforms (especially scour marks and teardrop shaped "islands") are the result of glacial flow rather than liquid flow. Teardrop shaped islands are common in terrestrial rivers, where the water is eroding material in the channel. A glacial feature called a drumlin has the exact same shape, but is formed by deposition beneath continental glaciers.

This VIS image illustrates the complex topography within Kasei Vallis. The smoother appearing section is the lowest in elevation and has been filled by deposition. To either side are eroded banks. The parallel striations running from lower-left to upper-right can represent: rock layers eroded to show the layering, terracing - erosion of the rock by different depths of flow, or scouring caused by material being ground against the banks by the downstream flow. Terracing is usually associated with action by liquid water; scour is generally associated with glacial (ice) flow.