The High Resolution Stereo Camera (HRSC), on board ESA's Mars Express spacecraft, operated by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR), captured image data from the Martian valleys Dao and Niger Valles over the course of eight separate orbits. This was then compiled into a vertical overview mosaic with a resolution of 25 metres per pixel. The mosaic extends over 755 kilometres north to south and 770 kilometres east to west, covering a total area of 581,350 square kilometres, roughly the size of the Iberian Peninsula.
The valleys are close to the Hesperia Planum volcanic region at latitude 32 degrees south and longitude 93 degrees east, on the imposing edge of the 2000-kilometre-wide Hellas impact basin. In Martian geology, such valley systems are known as ‘outflow channels’. The valleys are up to 40 kilometres wide in some places. The valley heads to the northeast are around 200 metres deeper than the valley outflows shown here. While the northern Dao Vallis is 2400 metres deep at its centre, the southern Niger Vallis has dug almost 1000 metres less into its surroundings. For this reason, the floor of the Niger Vallis exhibits a significantly more chaotic structure. The Niger Vallis is mostly dominated by terraced basin and rupture structures. In the Dao Vallis, a level valley floor with numerous, heavily eroded buttes in the valley interior is visible. The valleys are cut into a region that is still part of the southern slope of the Hadriaca Patera volcano, at the topmost edge of the image. Traces of numerous lava flows and possibly outflow channels can be made out on the surface.
As a joint undertaking by DLR, ESA and FU Berlin, the Mars Express HRSC images are published under a Creative Commons licence since December 2014: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO. This licence will also apply to all HRSC images released to date.