It has long been suspected that water might have once flowed across the surface of an ancient Mars. Previous evidence has been limited to disappearing and reappearing streaks spotted in satellite imagery, or analyzing the chemical composition of Martian soil to hunt for molecules associated with the presence of water. Now, new findings might definitively prove that Mars was once a wet, warm planet teeming with flowing water as opposed to containing only frozen glacial highlands.
According to a recent study published in Geology, astronomers from the Science & Technology Facilities Council and the UK Space Agency have discovered evidence of extensive riverbed formations stretching across the Martian surface. The riverbed system extends for over 17,000 kilometers (10,500 miles) throughout the Arabia Terra area of Mars’ northern hemisphere.
The riverbeds were spotted upon analysis of high resolution images gathered by NASA’s Mars Reconnaissance Orbiter. These ancient Martian riverbeds are on average 30m (100ft) high and up to 1–2km (.6-1.2 miles) wide. The published research claims that due to their arrangement and orientation, these riverbeds most likely show evidence of regularly flowing water as opposed to stagnant meltwater from high-altitude glaciers:
The inverted channels developed on extensive aggrading flood plains. As the inverted channels are both sourced in, and traverse across, Arabia Terra, their formation is inconsistent with discrete, localized sources of water, such as meltwater from highland ice sheets. Our results are instead more consistent with an early Mars that supported widespread precipitation and runoff.
In a press release issued by University College London, lead researcher Joel Davis stated that the data shows that Arabia Terra might have once been entirely submerged in water before becoming arid sometime in the distant cosmic past:
Arabia Terra was essentially one massive flood plain bordering the highlands and lowlands of Mars. We think the rivers were active 3.9–3.7 billion years ago, but gradually dried up before being rapidly buried and protected for billions of years, potentially preserving any ancient biological material that might have been present.
One of the sites along the floodplain is already being eyed for the 2020 ExoMars Rover mission currently being planned by the European Space Agency. Scientists will use the rover to gather more extensive geological data about the composition of Martian soil both on the surface and deep underground.