Tyras Vallis is an ancient river valley in the Lunae Palus quadrangle of Mars. It is located at 8.4 N° and 50.2° W. It was named after a classical name for the present Dniester River (in Ukraine).^[1]

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  Tyras Vallis Fan Deposit, as seen by HiRISE. Click on image to see layers.
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  Tyras Vallis Fan Deposit at a different sun angle. The scale bar is 500 meters long. This image is just to the right of the previous image.
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  Layers in Monument Valley. These are accepted as being formed, at least in part, by water deposition. Since Mars contains similar layers, water remains as a major cause of layering on Mars.