Picture this: a vast, barren plain of red dust billowing in the winds, with a giant, mysterious crater with fan-shaped sediment deposits fracturing the otherwise smooth landscape. This is the setting in which Perseverance, the NASA rover from the Mars 2020 mission, made its descent. Researchers from the Massachusetts Institute Technology (MIT) found that the crater, which they named Jezero, was an ancient lake — connected to a river system that existed 3.7 billion years ago.
The research, published on Thursday in Science, analyzed Perseverance’s images of Jezero taken from above: sediment patterns in the outcrop suggest that the crater was once a quiet lake. The study hypothesized that a dramatic climate shift caused cataclysmic floods, which hurtled the waterbody towards its end.
“Mars is currently cold and hyper-arid; liquid water is not stable at its surface. However, orbital and rover observations of features including valley networks, sedimentary fans, and ancient lake beds indicate the planet once had a warmer, wetter climate,” the paper stated.
Researchers inferred the crater’s origins to be a tranquil lake, based on the sediment deposits inclining into the crater. They took this to be evidence of “deltas that advanced into a lake.” Based on the sediment’s thickness, slope, and other features, scientists surmised that it must have been brought to the area by flowing water and not wind or other factors.
But in another section, the presence of massive rocks and boulders weighing up to several tons suggests that a high-energy flood may have brought them down from bedrock near the crater’s rim to the lakebed, eventually leading to the lake’s disappearance. The floods were no ordinary ones: researchers estimate they may have traveled at a speed of 9 meters carrying 3,000 cubic meters of water per second.
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“If you look at these images, you’re basically staring at this epic desert landscape. It’s the most forlorn place you could ever visit,” said Benjamin Weiss, a member of the team from MIT’s Department of Earth, Atmospheric and Planetary Sciences. “There’s not a drop of water anywhere, and yet, here we have evidence of a very different past. Something very profound happened in the planet’s history.”
What is exciting about the discovery is that it allows researchers to analyze samples from the craters for signs of ancient microbial life. The Mars 2020 mission will return Martian samples to Earth and will enable scientists to examine for biosignatures.
“We now have the opportunity to look for fossils,” Tanja Bosak, associate professor of geobiology at MIT and another team member, told Science Daily.
The discovery also prompts more interesting questions about what happened on Martian climate that triggered its trajectory to end up in its current form, completely arid and lifeless.
“The most surprising thing that’s come out of these images is the potential opportunity to catch the time when this crater transitioned from an Earth-like habitable environment to this desolate landscape wasteland we see now,” Weiss added.
The team hopes that the boulders may provide clues to what may have happened. But the question is also of urgent significance for Earth. Mars may well be a cautionary tale or a glimpse into our inevitable future with climate change. All in all, the red planet’s drastic transition from one type of landscape into another over billions of years could tell us something about the stories of planets everywhere, including the one we call home.
