Fast and furious floods from overflowing craters shaped the surface of Mars

Mars outlet crater

A topographic color image showing the river valleys of Mars. The Loire Vallis outlet canyon (white line) was formed from the overflow of a lake in the Paraná basin (outlined in white). Black lines indicate other river valleys formed by processes other than lake overflows. The background is a colored topography derived from the Mars Orbiter laser altimeter over a mosaic of images from the thermal emission imaging system. The image is approximately 650 kilometers wide. Credit: NASA / GSFC / JPL ASU

On Earth, river erosion is usually a slow process. But in MarsMassive flooding from overflowing crater lakes played a mammoth role in shaping the Martian surface, excavating deep chasms and moving large amounts of sediment, according to a new study led by researchers at the University of Texas at Austin.

The study, published today (September 29, 2021) in Nature, found that the floods, which probably lasted a few weeks, eroded more than enough sediment to completely fill Lake Superior and Lake Ontario.

“If you think about how sediments moved through the landscape on ancient Mars, the flooding of the lake breccias was a really important process globally,” said lead author Tim Goudge, assistant professor at the School of Geosciences of UT Jackson. “And this is a bit of a surprising result because they have long been considered unique anomalies.”

Goudge broke Mars Lake

The remains of an ancient crater lake on Mars surrounded by other smaller craters. The large exit canyon in the upper left was formed during a crater rupture event. Credit: Goudge et al.

Crater lakes were common on Mars billions of years ago, when the red planet had liquid water on its surface. Some craters could hold the water worth of a small sea. But when the water became too much to hold, it ripped through the crater rim, causing catastrophic floods that carved river valleys in its wake. TO Study 2019 led by Goudge determined that these events occurred quickly.

Remote sensing images taken by satellites orbiting Mars have allowed scientists to study the remains of broken Martian crater lakes. However, the crater lakes and their river valleys have mainly been studied individually, Goudge said. This is the first study to investigate how the 262 open lakes across the Red Planet shaped the Martian surface as a whole.

The research involved reviewing a pre-existing catalog of river valleys on Mars and classifying the valleys into two categories: valleys that began at the rim of a crater, indicating that they were formed during a flood in the lake gap, and valleys that were formed in other parts of the landscape, which suggests a more gradual formation over time.

Global map of the valleys of the river Mars

A global map of Mars showing the river valleys around the Red Planet. The river valleys formed by gaps in the crater lake are blank. River valleys that gradually formed over time are black. Credit: Goudge et al.

From there, the scientists compared the depth, length, and volume of different types of valleys and found that the river valleys formed by the crater lake bore well above their weight, eroding nearly a quarter of the volume of the Red Planet river valley despite constituting only 3% of the total length of the valley.

“This discrepancy is explained by the fact that the exit canyons are significantly deeper than other valleys,” said study co-author Alexander Morgan, a research scientist at the Institute of Planetary Sciences.

At 559 feet (170.5 meters), the average depth of a gap river valley is more than twice that of other river valleys created more gradually over time, which have an average depth of about 254 feet (77.5 meters). ).

Furthermore, although the chasms appeared in a geological instant, they may have had a lasting effect on the surrounding landscape. The study suggests that the breaches obliterated canyons so deep that they may have influenced the formation of other nearby river valleys. The authors said this is a possible alternative explanation for the unique topography of the Martian river valley that is generally attributed to climate.

The study shows that the river valleys of the lake gap played an important role in shaping the Martian surface, but Goudge said it’s also a lesson in expectations. Earth’s geology has removed most of the craters and makes river erosion a slow and steady process in most cases. But that doesn’t mean it will work that way on other worlds.

“When you fill [the craters] with water, there is a lot of stored energy to be released, ”said Goudge. “It makes sense that Mars may tilt, in this case, toward catastrophism more than Earth.”

Reference: “Importance of Lake Gap Flooding to Valley Incision on Early Mars” by Timothy A. Goudge, Alexander M. Morgan, Gaia Stucky de Quay, and Caleb I. Fassett, September 29, 2021, Nature.
DOI: 10.1038 / s41586-021-03860-1

The other co-authors of the study are Jackson Gaia School postdoctoral researcher Stucky de Quay and Caleb Fassett, a planetary scientist at the POT Marshall Space Flight Center.

NASA funded the research.

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