ESA's Mars Express Captures Images of River-Like Structure on Mars

A team of scientists from the European Space Agency (ESA) has discovered a river-like structure (images) on the Martian surface.

The agency's Mars Express captured striking images of a river-like structure in the upper Reull Vallis region of Mars. The river stretches for almost 932 miles (1,500 kms) across the Martian landscape. It is believed to have formed when running water was flowing through the Promethei Terra Highlands, adjacent to Reull Vallis, before running on to the floor of the vast Hellas basin, sometime in the Martian past.

The Promethei Terra Highlands include high and soft-rounded mountains rising around 2,500 m (nearly 8,200 feet) above the flat plains, and is surrounded by sediment-filled impact craters.

The river structure is bordered by numerous tributaries, but the 3-D images show only one of the tributaries of the river cutting through the valley. These images also show a region of Reull Vallis at a point where the river is more than 4 miles wide and almost 1,000 feet deep.

The river structures were likely formed by liquid water during the Hesperian period, between 3.5 billion and 1.8 billion years ago, and became dry due to evaporation, said the scientists.

"This region shows a striking resemblance to the morphology found in regions on Earth affected by glaciation. For example, we can see circular step-like structures on the inner walls of the sediment-filled crater in the foreground of the second perspective view. Planetary scientists think that these may represent former high water or glacial levels, before ice and water sublimated or evaporated away in stages at various times," the ESA said in a statement.

In September 2012, NASA's Curiosity rover found remnants of an ancient streambed on the surface of Mars, showing evidence that a stream once flowed across the region near the Gale Crater, which the rover is currently exploring.