As per ESA’s Mars Express team this structure was formed around 3.5 billion years ago. The images reveal a 1500 kilometre long river running from the Promethei Terra Highlands to the vast Hellas Basin. It is encompassed by many tributaries of which one can be seen cutting the main valley towards the upper north side. The image also shows that at a certain point the channel is 7 km wide and 300 metres deep.
Click on image to view full size (Image courtesy : ESA)
ESA also specified that the sides of Reull Vallis were sharp as well as steep as per the pictures captured by them. It consists of parallel longitudinal features covering the floor of the channel. It is believed that such structures were formed because of the passage of loose debris or ice during the Amazonian period caused by glacial flow along the channel. Experts from ESA were of the opinion that the images resembled the morphology which is found in various regions of the earth affected by glaciations. Thus a brief look into the distant past of the red planet shows that Reull Vallis has experienced certain things that are not too dissimilar to events on our world today.
[sources: 1,2]
