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Bursting the Dam

Today, most of the water on Mars is locked away in frozen ice caps. But billions of years ago it flowed freely across the surface, forming rushing rivers that emptied into craters. Research led by The University of Texas at Austin has found evidence that sometimes these crater lakes would take on so much water that they overflowed and burst from the sides of their basins, creating catastrophic floods that carved canyons very rapidly, perhaps in a matter of weeks.

The findings suggest that catastrophic geologic processes may have extensively shaped the landscape of Mars and other worlds that lack plate tectonics, said lead author Tim Goudge, an assistant professor in the Department of Geological Sciences at the Jackson School of Geosciences.

“These breached lakes are fairly common and some of them are quite large, some as large as the Caspian Sea,” said Goudge. “So we think this style of catastrophic overflow flooding and rapid incision of outlet canyons was probably quite important on early Mars’ surface.”

The research was published Nov. 16, 2018, in the journal Geology. Co-authors include NASA scientist Caleb Fassett and Jackson School Professor and Associate Dean of Research David Mohrig.

From studying rock formations in 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 carved by water that are tens to hundreds-of kilometers long.

However, until this study, it was unknown whether the canyons were carved over millions of years or rapidly by single floods. Using high-resolution photos taken by NASA’s Mars Reconnaissance Orbiter, the researchers examined 24 paleolakes and the topography of the outlets and the crater rims. They found a correlation between the size of an outlet and the volume of water expected to be released during a large flooding event. If the outlets had instead been gradually whittled away over time, the relationship between water volume and outlet size probably would not have held.

A similar process occurs on Earth when lakes dammed by glaciers break through their icy barriers. And whether on Earth or Mars, floods create outlets with similar shapes, the researchers found.

“This tells us that things that are different between the planets are not as important as the basic physics,” Goudge said.