Islands in Kasei Vallis (Released 27 April 2005)

Originating on the margin of Lunae Planum, the Kasei Valliscomplex contains two main channels that run east-westacross Tempe Terra and empty into Chryse Planitia.<p>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 proposedthat 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 <a href=&quot;http://www.zephryus.demon.co.uk/geography/resources/glaciers/drum.html&quot;>drumlin</a> has the exact same shape, but is formed by deposition beneath continental glaciers.<p>The upper portion of this VIS image contains several teardrop shaped "islands". If water cut these islands or ifglaciers deposited them, the thin tail points in the direction of flow. In this case, the flow was from upper left to the right. The scoured channel floor indicates that flow was to the right and upper right. The context image shows the multiple directions of flow in this region of the vallis.