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The sample collected by NASA’sExcitement as Mars rover drills first rock core for return to Earth
Perseverance rover might be volcanic, helping scientists to understand the red planet's evolution.
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An image taken from NASA’s Perseverance rover show a drilled hole in the surface of Mars
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| NASA's Perseverance rover drilled its first rock core on Mars on 6 August. The drill area appears as a small circular cone just to the right of the rover's shadow.Credit: NASA/JPL-Caltech |
Update: NASA announced late on 6 August that the rock core drilled by Perseverance failed to appear in its storage tube, despite initial data indicating that the tube processed as intended. NASA is assessing the situation to determine what went wrong. Nature will provide updates when they are available.
A robot on Mars has just collected the first-ever piece of Martian rock that is destined to be brought to Earth — and scientists are thrilled that it could be volcanic in origin. If confirmed, this means that, once the sample comes back to Earth, researchers could determine its age and gain insights into the planet’s fiery past.
After days of seeking the perfect spot to drill on the floor of Mars’s Jezero Crater and prepping it, NASA’s Perseverance rover collected the rock core, which is about the size of a piece of classroom chalk, on 6 August. The rover has been exploring the crater since landing there in February, with the goal of discovering whether life ever existed on the red planet.
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The core sample, which was drilled from a flat rock that looks like the kind of stone used to pave walkways, doesn’t contain any obvious signs of life. But it does hold a rich mix of tiny, multicoloured rock grains that were possibly created during an ancient meteorite impact or volcanic eruption. If and when the core arrives back on Earth — which would be no earlier than the year 2031, after a complex series of spacecraft retrieve it, along with other samples — researchers can analyse it to determine a precise date for when it formed.
“This core sample feels truly momentous,” says Meenakshi Wadhwa, a planetary scientist at Arizona State University in Tempe and NASA’s principal scientist for the joint NASA–European Space Agency effort to bring Perseverance’s cores back to Earth. “To me, it marks the beginning of Mars sample return — it finally feels real.”
The rover’s successful drilling marks a major accomplishment for the US$2.4-billion mission. It is the first step in collecting a series of 30 or more rock samples from across Jezero Crater, in an effort to build a library representing the geologic history of the area and any potential life that might once have existed there. Billions of years ago, Jezero was home to an ancient river delta and lake that could have been hospitable to life.
Image taken by NASA's Mars Perseverance rover of the surface of Mars
Prior to drilling, Perseverance dusted and lightly scraped the sampling area to reveal a variety of different-coloured minerals hinting that it might be volcanic rock.Credit: NASA/JPL-Caltech
If the samples are successfully collected and dated, it would be the first-ever pinpointing of the age of a rock on Mars. Scientists have evaluated the ages of Martian meteorites collected on Earth, but don’t know where exactly on Mars’s surface they came from — making it impossible to nail down an exact age for a specific set of rocks. Having a date from an intact rock would fundamentally transform scientific knowledge of the Martian surface.
Until now, scientists have been able only to guess at the ages of rock types on Mars, by estimating how many meteorite impacts have punched into them over time. With even just one dated rock to calibrate that, “we would make huge inroads to how we understand the timing of processes on Mars”, says Linda Kah, a geologist at the University of Tennessee in Knoxville and a member of Perseverance’s science team.
Igneous possibilities
The flat stones that Perseverance sampled cover part of the floor of Jezero Crater. Since leaving its landing site, the rover has driven about 1 kilometre across similar stones, which mission scientists are calling “cratered floor fractured rough”, a bland description that reflects how little they know about the rocks. For months, they have not been able to say whether these stones are igneous in origin — meaning they came from a volcanic eruption or other process involving molten rock — or sedimentary — meaning they were laid down, with one layer atop another, through a different geological process.
Now, however, many bets are on the rock being igneous, on the basis of initial appearances and preliminary data. Days before drilling the core, Perseverance dusted off and lightly scraped the stone at the spot it chose to drill — similar to polishing the surface of a dusty countertop to see what it looks like below the grime. That polished spot, around 45 millimetres across, revealed the astonishing array of multicoloured rock grains. “Just from the images, it looks like we have volcanic or igneous minerals,” says Kah. For instance, the whitish grains look like an igneous mineral known as feldspar.
An image taken from NASA’s Perseverance rover shows its robotic arm reaching out to examine rocks
Perseverance drilled and collected its first sample from Mars's Jezero Crater using its robotic arm.Credit: NASA/JPL-Caltech
Larger gaps that look like holes could be the remnants of gas bubbles, glass blobs, or other features that formed within molten rock before it solidified. Because igneous rocks form directly from molten rock, scientists can use the decay of radioactive minerals in the rock grains to determine when the rock cooled and crystallized, and thus its age.
“There’s a lot of excitement about it being a lava flow, potentially,” says Briony Horgan, a geologist at Purdue University in West Lafayette, Indiana, and a member of the rover’s science team. But much work remains to be done to confirm or refute these initial ideas by using more instruments aboard Perseverance that can, for instance, probe the rock’s mineralogy in different ways. Laboratory analyses on Earth will also reveal much more. “What’s really great about this mission is we’re going to get this rock back,” says Horgan.
Rolling onwards
The rover might collect a second core of the cratered floor fractured rough to have two samples for its core library, because the geology appears to be so important.
Perseverance will next head south along the crater floor and probably collect its next drill cores at a nearby area named Séítah, which is full of sand dunes, and an enigmatic region known as the Raised Ridges. Both represent different types of rock than the ‘paving stone’ that Perseverance has just drilled. The rover will probably keep exploring around Jezero’s floor until early 2022, and then will head towards the ancient river delta that is the mission’s ultimate target, collecting more cores as it goes.
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Perseverance is accompanied by a helicopter named Ingenuity, the first rotorcraft to ever fly on Mars. It has made 11 flights so far, often scouting terrain around the rover so that scientists can better see where they might want to explore next.
Other accomplishments since February include taking photographs of rocks in the distance that appear to be many tumbled boulders atop layers of more tranquil-looking sediment. Such formations suggest that one or more flash floods once ripped through Jezero, leaving jumbles of debris in their wake, the mission’s chief scientist, Ken Farley, said at a press briefing last month. He called it the most surprising finding of the mission to date.
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