* Astronomy

ESA's Mars Express orbiter captured this image with its High Resolution Stereo Camera that shows the Nanedi Valles valley system, a steep-sided feature that may have been formed in part by free-flowing water. The HRSC actually obtained the image on Oct. 3, 2004, during orbit 905 at a ground resolution of approximately 18 meters per pixel, but ESA has not released it until now.


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Credits: ESA/DLR/FU Berlin/G. Neukum

Nanedi Valles, a roughly 800-kilometre valley extending southwest-northeast and lying in the region of Xanthe Terra, southwest of Chryse Planitia. In this view, Nanedi Valles ranges from approximately 0.8- to 5.0-kilometre wide and extends to a maximum of about 500 metres below the surrounding plains. This valley is relatively flat-floored and steep-sloped, and exhibits meanders and a merging of two branches in the north. The valley's origins remain unclear, with scientists debating whether erosion caused by ground-water outflow, flow of liquid beneath an ice cover or collapse of the surface in association with liquid flow is responsible.

Image captured by the High-Resolution Stereo Camera (HRSC) onboard ESA's Mars Express on 3 October 2004 during orbit 905. North is to the right.