Nearly three years ago, NASA's Perseverance rover landed on Mars as part of a decades-long effort to investigate whether the now barren planet once hosted life.
Jezero crater once housed a large lake and a river delta. The size of a car Perseverance, equipped with advanced cameras and scientific instruments, has so far spent its days studying the environment and scooping up a variety of intriguing, 3.5 billion-year-old Martian rocks and soil scattered across the crater floor. As planned, the rover dropped ten sample-filled tubes on the ground, where they await the arrival of another robot that will take them back to Soil for more robust supervision in the 2030s.
On Tuesday (December 12), NASA announced that the $2.7 billion robotic explorer has fulfilled all its missions while delivering a good performance 1000 Martian days on the Red Planet. (One Martian day, or sol, lasts 24 hours and 37 minutes.) Initial analyzes of the rover's collected rocks show that some of them contained many carbonate-rich minerals and tiny silica grains, a combination that would likely have preserved all the organic molecules. of the era and prevented them from becoming degrading, similar to a "mummy grave," Morgan Cable of NASA's Jet Propulsion Laboratory (JPL) in Southern California told reporters at a press conference on Tuesday.
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Some rocks also show strong evidence for an intriguing mineral called iron phosphate. Here on earth, phosphate is in the DNA of all known life forms and also dissolves easily in liquid water. "We know that phosphorus is incredibly important," Cable said, "and now we have the strongest evidence ever gathered that phosphorus was available in a form that life would have access to if it were there."
"I would say mission accomplished," said Ken Farley, a geochemist at the California Institute of Technology in Pasadena who serves as project scientist for the Perseverance mission. "We got some very, very good samples."
Speaking at the American Geophysical Union (AGU) conference held this week in San Francisco and online, Farley said the 1,000-sol milestone also marks the start of a new bonus mission starting next spring that will take Perseverance to the edge from Jezero will bring. Crater, and possibly even beyond. Scientists suspect that ancient Martian groundwater in this region interacted with rocks in a way that created a completely different environment than what the rover has explored so far.
"It's actually quite remarkable that there is a route that we can take the rover on," Farley said, adding that Perseverance will roll 2.5 miles (4 kilometers) from its current location to reach the start of its exit path. "That gives us access to rocks that are much, much older."
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While next year's bonus tour is intended to fill the 13 sample tubes still on board the rover, the rocks collected so far are already helping scientists piece together pieces of how the Jezero crater is believed to have formed. by a asteroid impact about 3.9 billion years ago and later flooded by a long-lived river, evolved into the parched, boulder-strewn area that Perseverance shows us today.
The dramatic transformation took place in three major phases, Libby Ives, part of the Perseverance team at JPL, explained during Tuesday's briefing. Sometime about 3.7 billion years ago, a large, fast-moving river breached the crater rim and flowed in, carrying with it and leaving behind light-colored, fine-grained sand and mud, seen by Perseverance in an area called the nickname "the" Bacon strip Ives said.
The floodwaters then apparently filled the crater until the lake was about 100 feet deep, which can be inferred from the gradually changing layers of rock types plastered on top of each other, Ives said. The third and final phase witnessed another sudden colossal flood that threw round, 1 meter wide boulders over the crater.
"These are large rocks, probably not something you pick up yourself," Ives said.
At some point in Mars' history, the water that flooded the Jezero crater - and which also flowed into other parts of the planet - escaped into space, "never to be seen again," Farley said. "If that hadn't been the case, this would all be gone."
It is believed that the disappearance of surface water was accelerated by the frequent solar storms on the then young sun. removed Mars' once thick atmosphere. As the atmosphere became thinner and thinner, the planet lost more and more surface water, eventually becoming the icy desert we know today. (Mars' atmosphere is currently about 1% as thick as Earth's at sea level.)
Among the countless boulders that cover the surface of Mars today, scientists are particularly interested in fine-grained rocks at a site called Hidden Harbor, whose thin, white sulfate veins provide evidence of ancient water activity.
"This is the kind of rock that we pull apart grain by grain and study the individual grains very, very carefully," says Meenakshi Wadhwa of Arizona State University, who serves as lead scientist for the Mars Sample Return (MSR) mission. which aims to bring Perseverance's monsters to Earth.
"This would be one of the most daring robotic missions ever conducted," Wadhwa said. "It remains incredibly important because of its high strategic and scientific value."
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Scientists don't yet have a precise timeline for when Mars' surface was habitable and when it dried out, because that information can only be learned by dating rocks on Mars using equipment here on Earth. Robust analysis would also reveal whether the intriguing minerals Perseverance discovered are real evidence for life as we know it, and not just byproducts of physical processes.
In Tuesday's briefing, Lori Glaze, director of NASA's Planetary Science Division, emphasized the importance of returning samples collected by Perseverance to Earth. Studying that material in well-equipped labs around the world "is what will provide the ground truth for decades of remote sensing and in-situ data that we have exploring Mars," Glaze said.
NASA is leading the ambitious MSR mission, which aims to launch an orbiter and rocket lander in 2030, but remains under pressure due to cost overruns and unprepared architecture. In response to one report Of an independent review board urging a reconsideration of certain aspects of the design, Glaze said the mission team is currently evaluating several options to feasibly return those samples to Earth.
Under the current plan, Perseverance would load samples into the NASA lander, which would then launch the material into orbit around Mars. Above that, a European orbiter would pick up the sample capsule and tow it back to Earth. But the new bonus tour next year will take the rover beyond the crater rim and away from the original cache of samples on the crater floor, so team members still need to figure out exactly where the future sample-retrieval lander should land. Glaze said one option could be to drop the lander where Perseverance is currently located, or to drive the rover back to the crater floor near the fallen samples.
When those samples eventually reach Earth, they will be "preserved for decades and generations to come, so that scientists not yet born can answer questions we haven't yet thought of, using instruments not yet invented." Glaze said.
