Evidence of water in megacanyon on Mars

"Melas Chasma, a huge canyon forming part of the 4000 km Valles Marineris rift valley on Mars, plunges 9 km below the surrounding plains in this image, which was taken by the High Resolution Stereo Camera on the European Space Agency's Mars Express orbiter, making it one of the deepest depressions on the planet.

Released today by the German Aerospace Centre, the image also shows evidence that water once flowed and lakes once stood on the Martian surface. White lines are channels cut by water and lighter-coloured regions indicate deposits of sulphate components. Rock formations display evidence of flow textures, indicating that they were once deposited by liquid water, water ice or mud."

Read more at New Scientist (Thanks UKgnome)