In this VIS image, taken by the NASA - Mars Odyssey Orbiter on May, 7, 2013 and during its 50.555th orbit around the Red Planet, we can see a small section of the large and long (approx. 945 Km - such as about 586,84 miles) Southern Channel known as Reull Vallis. It has to be said that on the Bed (---> Floor) of several Martian Channels some Features called "Lineated Floor Deposits" can be found; these Features are (said in a very few words) just Ridged and Grooved Materials that seem to have deflected around obstacles, and Planetary Scientists believe them to be Ice-rich. In fact, even some Glaciers on our Home Planet Earth show such kind of Features and the Lineated Floor Deposits may also be related to the so-called "Lobate Debris Aprons", which have been proven to contain large amounts of Ice.
Said that, we have to highlight that Reull Vallis, as it can be easily seen in this beautiful picture, displays these Lineated Floor Deposits and, therefore, it is logical to assume that this Channel might have actually been carved, in a distant past of the Red Planet (such as eons ago), by liquid water that, for reasons which are still (and that, most likely, shall remain) unknown, slowly froze. For now, not much else can be said about these Surface Features but, maybe, in a Future (manned or unmanned) Mission to Mars these Features (as well as many other different ones) will - finally - be photographed, analyzed and then studied from very close and so, perhaps, a few more answers might even come...
Latitude (centered): 39,705° South
Longitude (centered): 109,896° East
This frame (which is an Original Mars Odyssey Orbiter b/w frame published on the NASA - Planetary Photojournal with the ID n. PIA 17330) has been additionally processed, magnified, contrast enhanced and then colorized in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Mars Odyssey Orbiter and then looked down, towards the Surface of Mars), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team.