The river is 1,500km long, once flowing on Mars

The European Space Agency (ESA) announced on January 17 a series of incredible images showing the clear traces of a giant river that once flowed on the surface of the Red planet.

Photos taken by ESA's Mars Express probe captured Reull Vallis ' image, a 'river-like structure' believed to have been formed when a large and strong water flowed on Mars in the past.

The ancient river formed a seamless deep channel that ran through the Promethei Tera plateau before reaching the bottom of the giant Hellas basin. Images provided by Mars Express show that the river is nearly 7 km wide and 300 meters deep.

Image of river bed running in Reull Vallis area.

The ancient river flows through the Promethei Terra plateau.

This incredible structure stretches to nearly 1,500km, nourished by a series of tributaries. Scientists believe that the river, which was formed long ago and originated in liquid state during the Hesperian period - is expected to end at about 3.5 billion -1.8 billion years ago. River water may have evaporated through different periods in the history of Mars.