Overflowing lakes carved canyons across Mars: Study

Water overflowing from ancient lakes on Mars created catastrophic floods that rapidly carved canyons on the red planet over three billion years ago, a study has found.

The findings suggest that catastrophic geologic processes may have had a major role in shaping the landscape of Mars and other worlds without plate tectonics, said Tim Goudge, a postdoctoral researcher at the University of Texas at Austin in the US.

"These breached lakes are fairly common and some of them are quite large, some as large as the Caspian Sea," said Goudge, lead author of the study published in the journal Geology.

"So we think this style of catastrophic overflow flooding and rapid incision of outlet canyons was probably quite important on early Mars' surface," he said.

From studying rock formations from satellite images, scientists know that hundreds of craters across the surface of Mars were once filled with water.

More than 200 of these "paleolakes" have outlet canyons tens to hundreds of kilometres long and several kilometres wide carved by water flowing from the ancient lakes.

However, it was unknown whether the canyons were gradually carved over millions of years or carved rapidly by single floods.

Using high-resolution photos taken by NASA's Mars Reconnaissance Orbiter satellite, the researchers examined the topography of the outlets and the crater rims and found a correlation between the size of the outlet and the volume of water expected to be released during a large flooding event.

If the outlet had instead been gradually whittled away over time, the relationship between water volume and outlet size likely wouldn't hold, Goudge said.

In total, the researchers examined 24 paleolakes and their outlet canyons across the Red Planet. One of the paleolakes examined in the study, Jezero Crater, is a potential landing site for NASA's Mars 2020 rover mission to look for signs of past life.

Researchers proposed the crater as a landing site based on prior studies that found it held water for long periods in Mars' past.

While massive floods flowing from Martian craters might sound like a scene in a science fiction novel, a similar process occurs on Earth when lakes dammed by glaciers break through their icy barriers.

They found that the similarity is more than superficial. As long as gravity is accounted for, floods create outlets with similar shapes whether on Earth or Mars.

Although big floods on Mars and Earth are governed by the same mechanics, they fit into different geological paradigms. On Earth, the slow-and-steady motion of tectonic plates dramatically changes the planet's surface over millions of years.

In contrast, the lack of plate tectonics on Mars means that cataclysmic events -- like floods and asteroid impacts -- quickly create changes that can amount to near permanent changes in the landscape.

"The landscape on Earth doesn't preserve large lakes for a very long time," said NASA scientist Caleb Fassett.

"But on Mars, these canyons have been there for 3.7 billion years, and it gives us insight into what the deep time surface water was like on Mars," Fassett said.