Selfie image of NASA’s Curiosity rover taken at Sol 2082 (June 15, 2018). A Martian dust storm reduces sunlight and visibility at the rover’s site at Gale Crater. Credit: JPL
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A new paper enriches scientists’ understanding of where the rock record has preserved or destroyed evidence of Mars’ past and possible signs of ancient life.
Today, Mars is a planet of extremes – very cold, highly irradiated, and very dry. But billions of years ago, Mars was home to a system of lakes that could sustain microbial life. As the planet’s climate changes, one of these lakes – in Mars’ Gale crater – is slowly drying up. Scientists have new evidence that very salty water, or brines, seeps deep through crevices, between soil grains at the bottom of dry lakes and turns mud. mineralRich layer underneath.
The results were published in the July 9 issue of the journal Science Led by the team responsible for chemistry and mineralogy, the CheMin instrument – aboard NASA’s Mars Laboratory Curiosity spacecraft – helps further understand where the rock record has been preserved or destroyed for evidence of Mars’ past and possible signs of ancient life.
“We used to think that once these clay mineral layers formed at the bottom of the lake at Gale Crater, they stayed that way, and maintained as they formed for billions of years,” said Tom Bristow, principal investigator and lead researcher at CheMin. . The authors of the research paper are at NASA’s Ames Research Center in California’s Silicon Valley. “But the salt water then destroys these clay minerals in places – essentially re-recording the rock.”
This flat layered rock imaged by the MastCam camera on NASA’s Curiosity Mars Rover shows a distinctive pattern of sediment deposition on the lake floor not far from where the water flows into the lake. Credit: NASA/JPL-Caltech/MSSS
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Mars: recorded in your permanent record
Mars has a treasure trove of rocks and minerals that are very ancient compared to Earth. And with the rock layers undisturbed in Gale Crater, scientists realized it would be an excellent site for searching for evidence of the planet’s history, and possibly life.
Using CheMin, the scientists compared samples from two areas about a quarter of a mile away from layers of mudstone deposited billions of years ago at the lake bottom at Gale Crater. Surprisingly, in one area, about half of the clay minerals they hoped for were gone. Instead, they found clay rock rich in iron oxide, the mineral that gives Mars its distinctive rust-red color.
Scientists know that the mudstone samples are about the same age and started at the same time – laden with mud – in both areas studied. Then why, as Curiosity explored the sedimentary clay deposits along Gale Crater, did the patching? clay minerals– And the evidence they keep – “disappeared”?
This network of cracks in Martian rock called “old cliffs” may have formed from the drying of clay layers more than 3 billion years ago. Credit: NASA/JPL-Caltech/MSSS
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Clay held the clue
Metal is like a time capsule. They provide records of what the environment was like at the time they were formed. Clay minerals contain water in their composition which is evidence that the soil and rock containing them have been in contact with water at some point.
“Because the minerals we find on Mars also form in several locations on Earth, we can use what we know about how they formed on Earth to tell us how salty or acidic water was on the ancient planet Mars,” said Liz Ramby, CheMin representative. . . Principal investigator and co-author at NASA’s Johnson Space Center in Houston.
Previous work revealed that while the Gale Crater lake is present and even after drying, groundwater moves beneath the surface, dissolving and transporting chemicals. After being deposited and buried, several claystone pockets undergo different conditions and processes due to interactions with these waters that change mineralogy. This process, known as “wetting”, often complicates or erases the previous history of the soil and writes a new one.
The mast camera (Mastcam) on NASA’s Curiosity Mars rover captured this mosaic while exploring the Mud Pad Module on February 3, 2019 (Sol 2309). The landscape includes a rocky landmark called “Knockfarril Hill” (center right) and Vera Rubin Ridge, which runs along the top of the landscape. Credit: NASA/JPL-Caltech/MSSS
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Diagenesis creates a supportive underground environment microbial life. In fact, some of the very unique habitats on Earth – where microbes thrive – are known as the “deep biosphere”.
“This is an excellent place to look for evidence of ancient life and measure habitability,” said John Grotzinger, research associate and co-author at the California Institute of Technology, or Caltech, in Pasadena, California. “Although sweat can erase signs of life in native lakes, it creates the chemical gradients needed to support life below the surface, so we were excited to find out.”
By comparing the mineral details of the two samples, the team concluded that the saltwater filtered through the upper sedimentary layers was responsible for the changes. In contrast to the relatively fresh water lakes found when the mudstones formed, the salt water is thought to have come from subsequent lakes in a generally drier environment. Scientists believe the findings provide additional evidence for the effects of climate change on Mars billions of years ago. It also provides more detailed information which is then used to guide Curiosity’s investigation into the history of the Red Planet. This information will also be used by NASA’s Mars 2020 Perseverance team as they evaluate and select rock samples to eventually return to Earth.
“We learned something very important: There are parts of Mars rekor rock This is not good at preserving evidence of the past and possible life of the planet, said Ashwin Vasavada, a Curiosity project scientist and co -author at NASA’s Jet Propulsion Laboratory in Southern California. craters, and mineralogy can be used to find out which ones. ”
Curiosity is in the early stages of investigating the transition to “sulphate bearing units,” or rocks believed to have formed during the drying of the Martian climate.
The gluconite-like clay found on Mars suggests that the planet has habitable conditions
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“Destruction of Clay Minerals by Salt Water at Gale Crater, Mars” Science (2021). science.sciencemag.org/cgi/doi… 1126 / science.abg5449–
Introduction
Jet Propulsion Laboratory
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quote: Curiosity Rover Finds Erased Rock Record Patch, Reveals Evidence (2021, 8 July) Accessed 8 July 2021 from https://phys.org/news/2021-07-curiosity-rover-patches-erased-revealing.html
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