Science

Catastrophic floods shaped Mars more than previously thought, scientists suggest

Catastrophic flooding from overflowing lakes on early Mars may have carved out many of the Red Planet’s valleys, a new study finds.

Although Mars is now cold and dry, decades of evidence suggest that it was once covered in rivers, streams, ponds, lakes, and perhaps even seas and oceans. A set of marks, all that water he left behind, comes in the form of a network of valleys etched all over the Red Planet. Previous research suggested that flowing water sculpted the web during an era that mostly ended between 3.5 and 3.7 billion years ago, and the new study offers another perspective on this era.

The work builds on previous research that suggested that more than 200 Martian lakes were filled with enough water to break open, leading to catastrophic flooding and carving canyons. Despite this evidence that such floods could help shape the Martian landscape at local scales, on a global level, scientists had previously explained the network of Martian valleys with long-lived rivers that caused more persistent gradual erosion.

Related: Photos: The Search for Water on Mars

The researchers behind the new study suspected that these floods may have played a larger role on the Red Planet than previously thought due to the highly crater nature of the Martian surface.

“The surface of Mars is covered in impact craters that act as perfect basins for ponds and storing water, which then provide numerous opportunities for large lake-breaking floods,” said lead study author Timothy Goudge, a planetary scientist at the University of Texas at Austin, he told Space.com.

Goudge and his colleagues analyzed valley networks on Mars, focusing on those carved during peak river activity on the Red Planet. The researchers focused on the valleys linked to the ancient lake basins, in particular the canyons that possessed floors with higher elevations than the floors of the lake basins where the two features connected, reasoning that the canyons probably formed when those lakes overflowed.

An ancient lake on Mars showing a canyon extending into the upper left corner. (Image credit: Goudge et al.)

The scientists then estimated the volumes these floods likely excavated from the shape and size of the features. The researchers found that flooding from the overflowing lakes likely formed about 13,675 cubic miles (57,000 cubic kilometers) in volume, more than 10 times the volume of Lake Michigan. That amount is equivalent to at least 24% of the total valley volume on Mars, even though such flood-carved canyons only account for about 3% of the total length of the valleys the researchers analyzed.

“Our finding that about a quarter of the volume of the valley on Mars was geologically carved out rapidly – on the order of days to months or years, as opposed to more than tens to hundreds of thousands of years – was actually quite surprising,” Goudge said.

Goudge noted that such floods “were certainly very important on Earth at specific times,” for example, when glaciers melted during the late Pleistocene, the time spanning from about 2.6 million to 11,700 years ago. The massive thaw overwhelmed many lakes, he said, and “great flooding from the glacial lakes carved out huge canyons in the Pacific Northwest.”

A global map of Mars distinguishes between canyons that researchers believe formed from crater lakes in white and river-eroded slow-forming canyons in black. (Image credit: Goudge et al.)

These new findings may have a major impact on scientists’ understanding of how the Martian landscape changed over time, Goudge said.

“For example, since the catastrophically formed lake outlet canyons are much deeper, they would have influenced longer-lived river valleys in the surrounding terrain, with the former acting as new conduits for the flow of water,” he said. “This is just one example of why catastrophic lake gap flooding really needs to be considered more consistently as we seek to understand the evolution of Martian river valleys.”

Going forward, Goudge and his colleagues intend to develop computer models of catastrophic lake-rupture flooding on Mars to shed light on the spatial and temporal dynamics of the phenomenon.

“For example, when we say that these cannons were carved quickly, we are often asked, ‘How fast is fast?'” Goudge said. “For this current study, all we can say is that it was geologically fast, where the difference between three days and three months or even three years is essentially negligible compared to tens or hundreds of thousands of years.”

The scientists detailed their findings online September 29 in the journal Nature.

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