Nearly three years ago, NASA’s Perseverance rover landed on Mars as a part of a decades-long effort to check if the now-barren planet ever hosted life.
Jezero Crater once harbored an enormous lake and a river delta. The car-sized Perseverance, equipped with sophisticated cameras and science instruments, has to this point been spending its days studying its environs and scooping up quite a lot of intriguing, 3.5-billion-year-old Martian rocks and soil scattered on the crater floor. As planned, the rover has dropped 10 sample-filled tubes on the bottom, where they await the arrival of a distinct robot which is able to ferry them back to Earth for more robust scrutiny within the 2030s.
On Tuesday (Dec. 12), NASA announced that the $2.7 billion robotic explorer has fulfilled all its assignments while also notching 1,000 Mars days on the Red Planet. (One Mars day, or sol, lasts 24 hours and 37 minutes.) Initial analyses of the rover’s collected rocks reveal that a few of them contain loads of carbonate-rich minerals and minuscule silica grains, a mix that likely would have preserved any organic molecules from the time and prevented them from degrading, akin to a “mummy’s tomb,” Morgan Cable, of NASA’s Jet Propulsion Laboratory (JPL) in Southern California, told reporters during a press briefing on Tuesday.
A few of the rocks also show strong evidence for an intriguing mineral called iron phosphate. Here on Earth, phosphate is present in the DNA of all known life forms and in addition dissolves easily in liquid water. “We all know that phosphorus is incredibly vital,” said Cable, “and now we’ve the strongest evidence ever collected that phosphorus was available in a form that life could access if it was there.”
“I’d say, mission completed,” said Ken Farley, a geochemist on the California Institute of Technology in Pasadena who serves because the project scientist for the Perseverance mission. “We have acquired some very, superb samples.”
Speaking on the American Geophysical Union (AGU) conference being held this week in San Francisco and online, Farley said the 1,000-sol milestone also marks the start of a brand new bonus mission starting next spring that may take Perseverance up and across the rim of Jezero Crater, and possibly even beyond. Scientists suspect that ancient Martian groundwater on this region interacted with rocks in a way that created an environment completely different from what the rover has explored to this point.
“It’s quite remarkable actually that there’s a route that we will drive up with the rover,” said Farley, adding that Perseverance will roll 2.4 miles (4 kilometers) from its current location to achieve the beginning of its egress path. “That may allow us access to rocks which can be much, much older.”
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While the bonus trek next yr will aim to fill the 13 sample tubes remaining onboard the rover, the rocks collected to this point are already helping scientists stitch together pieces of how Jezero Crater, thought to have been birthed by an asteroid impact about 3.9 billion years ago and later flooded by a long-lived river, evolved to be the parched, boulder-strewn area Perseverance is showing us today.
The drastic transformation occurred across three major phases, Libby Ives, a part of the Perseverance team at JPL, explained during Tuesday’s briefing. Sometime around 3.7 billion years ago, a big, fast-moving river breached the crater’s rim and gushed in, carrying with it — and abandoning — light-colored, fine-grained sand and dust seen by Perseverance in an area nicknamed the “Bacon Strip,” Ives said.
Floodwaters then apparently filled the crater until the lake was 100 feet (30 meters) or so deep, which will be inferred from the step by step changing layers of rock types plastered onto each other, said Ives. The third and final phase witnessed one other sudden colossal flood that dumped round, 3.3-foot-wide (1 m) boulders across the crater.
“These are big rocks, probably not something you are picking up by yourself,” said Ives.
Sooner or later in Mars’ history, the water flooding Jezero Crater — and flowing in other parts of the planet — escaped into space, “never to be seen again,” said Farley. “Had that not been the case, this might all be gone.”
The surface water’s disappearance is believed to have been accelerated by the then-young sun’s frequent solar storms, which stripped away Mars’ once-thick atmosphere. As its atmosphere got thinner and thinner, the planet lost more and and more of its surface water, eventually becoming the frigid desert we all know today. (Mars’ atmosphere is currently about 1% as thick as Earth’s is at sea level.)
Amongst countless boulders cluttering the Martian surface today, scientists are particularly keen on fine-grained rock at a spot named Hidden Harbor, whose thin, white sulfate veins are evidence for ancient water activity.
“That is the sort of rock that we’d pull apart grain by grain and really study individual grains very, very fastidiously,” said Meenakshi Wadhwa of Arizona State University, who serves because the principal scientist for the Mars Sample Return (MSR) mission, which goals to bring Perseverance’s samples to Earth.
“This is able to be some of the audacious robotic missions ever conducted,” said Wadhwa. “It stays incredibly vital for its high strategic and scientific value.”
Scientists don’t yet have a precise timeline for when Mars’ surface was habitable and when it became parched, as that information will be learned only by time-dating Martian rocks using equipment here on Earth. Robust evaluation would also reveal if the intriguing minerals that Perseverance has spotted are really evidence for all times as we comprehend it and not only 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. Study of that material in well-equipped labs all over the world “is what is going to provide the bottom truth for a long time of distant sensing and in-situ data that we’ve from exploring Mars,” Glaze said.
NASA is spearheading the ambitious MSR mission, which goals to launch an orbiter and rocket-toting lander in 2030 but stays under stress as a result of its cost overruns and unprepared architecture. In response to a report from an independent review board that urged a rethink of certain facets of the design, Glaze said the mission team is currently evaluating different options to feasibly return those samples to Earth.
As per the present plan, Perseverance would load samples into the NASA lander, which might then launch the fabric to Mars orbit. Up there, a European orbiter would grab the sample capsule and haul it back toward Earth. But the brand new bonus trek next yr will move the rover outside the crater’s rim and away from its initial stash of samples on the crater floor, so team members are yet to work out exactly where the long run sample retrieval lander should touch down. Glaze said one option could also be to perch the lander wherever Perseverance is at the moment, or drive the rover back to the crater floor near the dropped samples.
When those samples ultimately reach Earth, they can be preserved “for a long time and generations to return in order that scientists who have not even been born yet can address questions we’ve not considered yet, using instrumentation that hasn’t been invented,” said Glaze.