Combining information from the High-Resolution Stereo Camera (HRSC) and recent color channel data, the European Space Agency (ESA) stitched together this view of the Reull Vallis on Mars.
The image delivers striking evidence to Mars' watery past, with the riverlike channel showing signs of being formed by running flowing water. The surrounding landscape is hypothesized to once have been rolling highlands with smooth plains, the Reull river tributaries cutting through the terrain.
ESA scientists place the valley itself at a width of over four miles and a depth nearing 1,000 feet. Linear features on the valley floor were mostly likely formed by debris and ice in a process similar to the formation of glacial valleys here on Earth.
Using the color-coded version of the image (below) the ESA model shows off the topography of the Reull Vallis. The depth of the main channel is coded in blue, which contrasts drastically with the nearby red heights of Promethei Terra Highlands and their smooth, rounded mountaintops.
Using the information provided by the HRSC, the ESA created a computer-generated perspective of the Reull Vallis. From this angle the viewer can plainly see a tributary branch of the river breaking off to the left.