Massive Cliffs in Echus Chasma
At over 100 kilometers long and 10 kilometers wide, it's a huge canyon -- although it is dwarfed by its companions to the south (Valles Marineris - which extends 4,000 kilometers from east to west) and north (Kasei Valles - which extends 3,000 kilometers to the north).
And lining the sides of Exhus Chasma are massive cliffs - which contain layers of clay.
A clear indication that this area once contained a huge amount of water.
In fact, the leading theory is that this area was once one of the the largest sources of water on the planet.
Is that what caused the massive cliffs? Did water rush down the length of the surface and carve the canyon on its way to Kasei Valles?
If true, water once held in Echus Chasma likely ran over the Martian surface to carve the deep gorges of Kasie Valles to the north.
But even if water carved this canyon, it appears lava may have also been a contributor to its formation -- the floor of the canyon is extremely smooth, indicating potential lave flows.
Not surprising, since this valley lies just to the east of the Tharsis plateau and its massive volcanoes.
This image was taken by the Mars Express orbiter on July 23, 2008.