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The Gale crater on Mars contained a lake, or a series of lakes, a few billion years ago. The streams once emptied into this lake. Now, new evidence from the Curiosity rover suggests giant flooding has passed through this region as well. Computer generated image via Flickr user Kevin Gill. Check out more computer graphics by Kevin depicting Martian lakes and rivers.
NASA’s Curiosity rover has been exploring the Gale crater on Mars since 2012. At that time, it was confirmed that a lake – or a series of lakes and streams – existed a few billion years ago. This is further proof that Mars was once a wetter and much more habitable environment than it is today. On November 18, 2020, scientists announced a new study based on analysis of data from Curiosity that provided yet another glimpse into Gale Crater’s past: mega floods. These are giant floods, probably caused by a meteorite impact, which passed through the crater with incredible power, leaving behind ripples that can still be seen today.
The researchers – from Cornell University, Jackson State University, the Jet Propulsion Laboratory and the University of Hawaii – published the new peer-reviewed findings in Scientific reports November 5, 2020.
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These scientists said heat from a meteorite impact likely created the mega-floods by melting ice on the Martian surface. The find is a bit surprising, as the telltale geological structures were first seen by Curiosity, and had not previously been identified from orbit, as co-author Alberto G. Fairén stated:
We identified mega-floods for the first time using detailed sedimentological data observed by the Curiosity rover. The deposits left by the mega-floods had not previously been identified with the orbiter’s data.
View of the buttresses and buttes at the base of Mount Sharp in Gale Crater. The colors in this image have been enhanced to look more like Earth, making it easier for scientists to see the different layers of stratification in the hills. Curiosity has found huge wave-shaped features in the sedimentary layers of the crater, indicating that huge mega-floods once passed through here. Image via NASA / JPL / Cornell University.
The rover found giant wave-like features in the sedimentary layers of Gale Crater. The features – called megaripples (a sort of sedimentary ripple mark) or antidunes – are about 9 meters high and are spaced about 450 feet (about 140 meters) apart. They are evidence of mega-flooding at the bottom of the crater about 4 billion years ago. Their appearance is surprisingly similar to the characteristics of the Earth created by the melting ice some 2 million years ago.
According to scientists, a big impact was the cause of the mega-floods, but how did it happen?
The impact not only melted the ice, but also released carbon dioxide and methane, which had been frozen and trapped below the surface. This combination created warmer and wetter conditions for a short period of time. The resulting condensation in the atmosphere formed clouds of water vapor similar to those on Earth. From these clouds came torrential rains over much of the planet.
Alberto G. Fairén of Cornell University, co-author of the new study. Image via Cornell University.
In the case of Gale Crater, rainwater combined with other water from Mount Sharp, the large mountain in the middle of the crater that Curiosity is now exploring at its base. All of that water produced huge flash floods which created the ripple characteristics that we can still see today. This includes the gravel ridges in the Hummocky Plains unit and the ridge and trough band formations in the ridged unit.
The geological clues left behind reveal an environment in Gale Crater much different from what we see now. It’s hard to imagine giant flooding in Gale Crater, but geological evidence shows it has happened.
Earlier evidence from Curiosity had also confirmed the earlier presence of long-lived lakes in the crater, as well as streams flowing into it. Fairén said:
The beginning of Mars was an extremely geologically active planet. The planet had the necessary conditions to support the presence of liquid water on the surface, and on Earth, where there is water, there is life. So early on, Mars was a habitable planet. Was it inhabited? That’s a question the next Perseverance rover… will help answer.
Schematic representation of the direction of flow of waves and antidunes (megaripples) in Gale Crater about four billion years ago. Image via E. Heydari et al./ Nature/ Scientific reports/ Attribution 4.0 International (CC BY 4.0).
Comparison of ancient gravel from the stream bed in Gale Crater on Mars (left) with an example on Earth (right), further evidence that water once gushed through the crater billions of years ago ‘years. Image via NASA / Phys.org.
Partial view of the Ares Vallis landscape around the Pathfinder lander in 1997. The hills of Twin Peaks can be seen in the distance, and most of the larger boulders are tilted in the same direction, evidence of massive flooding in the past . Image via NASA / JPL / Timothy Parker.
Evidence of flash flooding has also been seen elsewhere on Mars, from above, by orbiting spacecraft. NASA’s Pathfinder mission, which landed at Ares Vallis in 1997, also saw small rounded pebbles and larger boulders tilted in the same direction and stacked up, all evidence of massive flooding in the distant past. Curiosity results now add to all of this, with additional in situ measurements from the ground. Curiosity even studied the ancient gravel of the stream beds, still in place after being deposited by streams flowing into Gale Crater a few billion years ago.
With giant floods, lakes and streams, Gale Crater was once a many different place. It was certainly habitable, at least for germs. We still don’t know if something ever lived there, and the rover isn’t equipped to tell us, but the more Curiosity explores, the more it seems possible. But even though there were no small creatures to witness it back then, the landscapes of Gale Crater and other places have been forever changed by those raging waves long ago.
Bottom line: NASA’s Curiosity rover has found evidence of ancient giant flooding in Gale Crater on Mars.
Source: Giant flood deposits in Gale Crater and their implications for early March climate
Via Cornell University
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