According to a new study, catastrophic floods caused by lake overflows at the beginning of Mars may have created many valleys on the Red Planet.
While Mars is now cold and dry, decades of evidence suggest it was once covered with rivers, streams, ponds, lakes, and possibly even seas and oceans. A bunch of marks all this water left behind come in the form of a network of valleys engraved on the red planet. Previous research suggested that flowing water carved the network during an era that mostly ended about 3.5 billion to 3.7 billion years ago. The new study offers another perspective on this time.
The work builds on previous research that suggests that more than 200 Martian lakes are filled with enough water to breach, triggering catastrophic flooding and sculpting 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 Martian valley network with long-lived rivers that caused more persistent gradual erosion.
The researchers behind the new study suspected that these breach floods might have played a more critical role on the Red Planet than previously thought because of the highly cratered nature of the Martian surface.
"The surface of Mars is covered in impact craters that act as perfect basins to pond and store water in, which then provide numerous opportunities for large lake-breach floods," study lead author Timothy Goudge, a planetary scientist at the University of Texas at Austin, told Space.com.
Goudge and his colleagues analyzed the valley networks on Mars, focusing on those sculpted during the peak of fluvial activity on the Red Planet. The researchers focused on valleys linked to ancient lake basins, particularly canyons that possessed floors with elevations higher than the floors of the lake basins were the two features connected, reasoning that the gullies likely formed when those lakes overflowed.
The scientists then estimated the volumes that these floods likely dug up based on the shape and size of the features. The researchers found that flooding from overflowing lakes probably caused about 13,675 cubic miles (57,000 cubic kilometers), or more than ten 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-excavated canyons only represent about 3% of the entire length of the valleys the researchers analyzed.
"Our finding that approximately one-quarter of the valley volume on Mars was carved geologically rapidly — on the order of days to months to years, as opposed to over tens to hundreds of thousands of years — was indeed quite surprising" Goudge said.
Goudge noted such lake-breach floods "were certainly very important on Earth at specific times," for instance, when glaciers melted during the end of Pleistocene, the epoch spanning from about 2.6 million to 11,700 years ago. The massive melting flooded many lakes, he said, and "great glacial flooding of carved lake huge canyons across the north-western Pacific."
These discoveries could have far-reaching implications for scientists' understanding of how the Martian landscape has changed over time, said Mr. Goudge.
"For example, since the catastrophically formed lake outlet canyons are so much deeper, they would have influenced the longer-lived river valleys on 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 flooding from a lake breach needs to be considered more systematically as we seek to understand the evolution of the valleys of the Marianne River."
In the future, Goudge and his colleagues aim to develop computer models of catastrophic lake breccia floods on Mars to shed light on the spatial and temporal dynamics of the phenomenon.
"For example, when we say that those canyons were quickly sculpted, we are often asked, 'How fast is fast? '" Goudge says. '" Goudge said. "For this present study, all we can say is that it was geologically rapidly, 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."