Dramatic dried river canals over a mile wide and 650 meters deep have been discovered on Mars, showing how the red planet once hosted liquid water at its surface.
We know Mars today as a crazy wasteland, but for about 3.4 billion years ago, the red planet was blown in blue, with a large sea in its northern hemisphere, lakes and many winding rivers. During his old past, Mars had a thick and warm atmosphere that allowed the planet to maintain liquid water at the surface. Observations from satellites in orbit around Mars and robbers on the surface have provided evidence of this, whether in the form of dried river beds or clay-like deposits requiring the formation of water.
Eventually, the thick martial atmosphere, and with it, deepened the planet's surface water. Today, visible evidence of this water can still be seen as frozen on the poles.
New images released by the European Space Agency (ESA) today offer further evidence of Mars' watery past. The region shown in the pictures is a system of valleys located in the southern highlands, just east of a large battleground called Huygens. The images, captured by ESA's Mars Express satellite late last year, show an old, highly-cradled region that, despite eons of erosion, still shows talent signs of liquid water.
Water has once flowed down the north (right to left in the picture), which gives rivers as wide as two kilometers (1.2 miles) and as deep as 200 meters, according to ESA. Today, the valley is smooth and fragmented, but its former status as a riverbed is clearly visible. ESA further explains:
Everywhere the valley system seems to be delimited and forms a pattern that resembles tree branches originating from a central luggage. This type of morphology is known as "dendritic" – the term derived from the Greek word for tree (dendron), and it is easy to see why. Different canals are divided from the central valley and form small tributaries that are often divided again on their journey outwards.
This type of dendritic structure is also seen in sewage systems on earth. A particularly good example is that of the Yarlung Tsangpo River, which flows from the source of western Tibet down through China, India and Bangladesh. In the case of this image of Mars, these branch channels were probably formed by the surface water runoff from a once strong river flow combined with extensive precipitation. This flow is considered to have cut through existing terrain on Mars, forging new roads and carving a new landscape.
The presence of rushing old water on Mars raises many questions. What was the source of this rushing water? Was it caused by melting glaciers, or was water pouring out under the surface? Or did rain generate the liquid water? And how long was this water before it dried up? Essentially, did this water contribute to livable conditions on Mars, and did life once see the planet?
These questions are unanswered and serve as rallying calls for more studies to be done by Mars. Fortunately, NASA's curiosity and InSight landers continue to gather valuable data, as well as NASA's Mars Reconnaissance Orbiter and ESA's ExoMars Trace Gas Orbiter and Mars Express. And we also have the upcoming ExoMars mission to look forward to, which will include the newly named Rosalind Franklin rover.