An ancient riverbed - on Mars

London, Jan 18: New astonishing pictures by the European Space Agency have revealed a 1500 km long and 7 kilometre wide river that once ran across Mars... The agency’s Mars Express imaged the striking upper part of the remnants of Reull Vallis river on Mars with its high-resolution stereo camera...

This sinuous structure, which stretches for almost 1500 km across the martian landscape, is flanked by numerous tributaries, one of which can be clearly seen cutting in to the main valley towards the upper (north) side.

The new Mars Express images show a region of Reull Vallis at a point where the channel is almost 7 km wide and 300 m deep. The sides of Reull Vallis are particularly sharp and steep, with parallel longitudinal features covering the floor of the channel itself.

These structures are believed to be caused by the passage of loose debris and ice during the “Amazonian” period – which continues to this day – due to glacial flow along the channel. The structures were formed long after it was originally carved by liquid water during the Hesperian period, which is believed to have ended between 3.5 billion and 1.8 billion years ago.