The High Resolution Stereo Camera on ESA’s Mars Express spacecraft has highlighted details of the fast-flowing water and catastrophic flooding that carved a gorge south of the southeastern rim of the vast Valles Marineris canyon system. The image above shows the central portion of Osuga Valles, an outflow channel that empties into a region of chaotic terrain in a 2.5km deep depression (shown in the lower part of the images, in yellow and green). The water may have formed a lake there, or simply soaked into the surface. Osuga Valles shows erosion patterns characteristic of fast-flowing water, such as sets of parallel narrow grooves in the valley floor. The direction of flow is indicated by the streamlined shapes of the islands and the gradient of the valley floor. The HRSC images are also detailed enough to show elevation changes and cross-cutting relationships of channels around the islands, indicating that there were several episodes of flooding.
This image is published in the June 2014 issue of Astronomy & Geophysics.