Sustained storms worldwide with lakes, rivers on ancient Mars have filled up

A new study from the University of Texas at Austin helps scientists bring together the ancient climate of Mars by revealing how much precipitation and snowmelt filled its marginal beds and river valleys 3.5 billion to 4 billion years ago.

The study, published in Geology, represents the first time scientists have quantified the landslide that must have occurred across the planet, and it turns out when the Mars 2020 Perseverance rover makes its way to the red planet to land in one of the mare beds of crucial importance to this new study.

The ancient climate of Mars is something of a science for scientists. For geologists, the existence of river beds and paleolakes – centuries-old streams) paints a picture of a planet with significant precipitation as snowmelt. But scientists specializing in computer climate models of the planet have not been able to reproduce an ancient climate with large amounts of liquid water present for long enough to account for the observed geology.

“This is extremely important because 3.5 to 4 billion years ago Mars was covered with water. It had a lot of rain or snowmelt to fill those canals and lakes,” said lead author Gaia Stucky de Quay, a postdoctoral fellow. at UT’s Jackson School of Geosciences. “Now it’s completely dry. We’re trying to understand how much water there was and where it all went.”

Although scientists have found large amounts of frozen water on Mars, there is currently no significant amount of liquid water.

In the study, researchers found that precipitation must have been between 13 and 520 feet (4 to 159 meters) in a single episode to fill the lakes and, in some cases, provide enough water to flood the lakes’ streams. and to break. Although the range is large, it can be used to understand which climate models are accurate, Stucky de Quay said.

“It’s an enormous cognitive dissonance,” she said. “Climate models are having problems on account of that amount of liquid water at the moment. It’s like, liquid water is not possible, but it happened. This is the knowledge gap that our work is trying to fill.”

Scientists looked at 96 lakes with open basins and closed basins and their watercourses, all thought to have formed between 3.5 billion and 4 billion years ago. Open lakes are those that are flooded by floodwaters; locks, on the other hand, are intact. Using satellite imagery and topography, they measured areas of lake and watershed, and volumes of lake, and calculated possible evaporation to determine how much water was needed to fill the lakes.

By looking at ancient closed and open lakes, and the river valleys that feed them, the team was able to determine a minimum and maximum rainfall. The closed lakes offer a glimpse of the maximum amount of water that could have fallen in one event without breaking the side of the naval basin. The open lakes allow the minimum amount of water required to cross the water basin, causing the water to break and eject into a side.

In 13 cases, researchers discovered coupled basins – which contained one closed basin and one open basin that were fed by the same river valleys – which provided important evidence of both maximum and minimum precipitation in one event.

Another big unknown is how long the episode as a snowmelt episode must have lasted: days, years or thousands of years. That’s the next step in the investigation, Stucky de Quay said.

While this study is being published, NASA recently launched Mars 2020 Perseverance Rover to visit Jezero Crater, which contains one of the open lake beds used in the study. Co-author Tim Goudge, an assistant professor in the UT Jackson School Department of Geological Sciences, was the chief scientific advocate for the landing site. He said the data collected by the crater could be significant in determining how much water was on Mars and whether there are signs of past life.

“Gaia’s study takes previously identified closed and open lake basins, but applies a clever new approach to limit how much rainfall these lakes have experienced,” Goudge said. “Not only will these results help us improve our understanding of the ancient Mars climate, but they will also be a great resource for placing the results of the Mars 2020 Perseverance Rover in a more global context.”