In 2012, the European Space Agency discovered a huge 1,500 kilometer river in the upper Reull Vallis region of Mars.
The agency’s Mars Express took a picture of the area using a high-stereo camera, which gave an impressive look at the landscape. Now it has released the 3D image taken of the river, which shows a large area of the Reull Vallis complete with one tributary and mountains off to the right.
According to scientists, the river was likely formed by water in the Hesperian period between 1.8 and 3.5 million years ago. Although only one is visible in the image, multiple tributaries meet the river, with the one pictured branching off in the main valley and re-merging upstream. The part of the river pictured is nearly 300 meters deep and 7 kilometers wide.
Visible to the right of the river and tributary are the Promethei Terra Highlands, which include the almost putty-like mountain ranges that appear hyper-smooth and rounded. The mountains are about 2,500 meters above the land’s surface, and are surrounded by impact craters, one of which has a diameter nearly are large as the mountain it is near.
The scientists note that the river contains elements reminiscent of what you would find on Earth, with “step-like structures” in the craters indicating high water. Likewise, the morphology indicates that the area experienced glacial activity in its past, and provide the researchers with a relatively detailed look at events in the Red Planet’s past that helped shape it.