European Space Agency Discovers Billion Year Old River on Mars

Analysing high-resolution 3D images taken in 2012 by the Mars Express stereo camera, the European Space Agency astronomers verified that the region Reull Vallis contains a river-like structure. They believe it was formed when running water flowed in the distant martian past, cutting a steep-sided channel through the Promethei Terra Highlands before running on towards the floor of the vast Hellas basin, as seen in the Mars images below.

The river-bed is almost 1500 kilometer long, running across the martian landscape. The new Mars Express images show a region of Reull Vallis at a point where the channel is almost 7 kilometer wide and 300 meter deep.

In the wider context image, a tributary intersecting the main channel appears to be part of a forking of the main valley into two distinct branches further upstream before merging back into a single main valley.

The right (northern) part of the main image is dominated by the Promethei Terra Highlands with their high and soft-rounded mountains shown in these images, rising around 2500 m above the surrounding flat plains.

The sides of Reull Vallis are particularly sharp and steep in these images, 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. Similar lineated structures, believed to be rich in ice, can also be found in many of the surrounding craters.

This region shows a striking resemblance to the morphology found in regions on Earth affected by glaciation. The morphology of Reull Vallis suggests it has experienced a diverse and complex history, with analogies seen in glacial activity on Earth. These analogies are giving planetary geologists tantalising glimpses of a past on the Red Planet not too dissimilar to events on our own world today.