The latest images transmitted by the High Resolution Stereo Camera aboard ESA's Mars Express spacecraft reveal a region called Libya Montes, south of the Isidis Planitia impact basin on the red planet.
The images show the central reaches of a 400-kilometer (250-mile) long valley carved into the surface in early Martian history, approximately 3.5-billion years ago.
The valley's central parts show traces of an interior valley clearly documenting the flow of water that once occurred on the surface of the planet during periods of wetter climate.
The HRSC obtained the images during orbit 922, with a ground resolution of approximately 14.3 meters (46.5 feet) per pixel at equatorial latitudes near longitude 81 degrees east. ESA scientists said based on high-resolution HRSC-derived digital terrain models, water-discharge rates in the valley would have been comparable to those of the middle reaches of the Mississippi river in the United States.
On the basis of crater-size frequency distributions on the valley floor and surrounding terrain, scientists estimate the valley was formed over a time period of about 350 million years. Measurements of erosion rates suggest the active phases of valley development were characterized by short periods of intense flows, rather than more moderate sustained flows.
