Although we think of Mars as a dry and dusty wasteland, it once contained enormous amounts of water on its surface.
Newly released images from the European Space Agency (ESA) provide more evidence of the Red Planet's previous incarnations — which included water on what was a warmer planet around 3.5 billion years ago.
The photos, taken by the ESA's Mars Express satellite, show an ancient region in the southern highlands of Mars filled with craters that have markers of flowing water. The space agency says the region's topography suggests that water flowed downhill from north to south, carving out valleys up to 1.2 miles across and 656 feet deep as it did so.
"We see Mars as a cold, dry world, but plenty of evidence suggests that this was not always the case. Research in past years instead increasingly indicates that the planet once had a thicker, denser atmosphere that was able to lock in far greater amounts of warmth, and therefore facilitate and support the flow of liquid water on the surface below," the ESA said in a statement.
It's still unclear, according to scientists, where the water on the Red Planet came from. The possibilities include groundwater, precipitation or even melting glaciers.
A question that follows naturally from the discussion of water is, Could Mars have been suitable for life forms?
In search of an answer, next year ESA and Roscosmos will launch the ExoMars mission comprising a rover – recently named Rosalind Franklin – and a surface science platform. The rover will drive around the planet and drill below the surface in search of signs of life.
Meanwhile, the Red Planet's landscape will continue to fascinate scientists and cause widespread awe.