Mars is cold and dry today, but billions of years ago, liquid water existed on its surface, and scientists have long been curious about what it was like back then. New Researchpublished in Communication Earth and the Environment The July 7 Mars mission examined data from soil samples collected by NASA’s Curiosity rover and compared it to similar soils on Earth, providing clues about what the Martian surface was like billions of years ago, with the data suggesting that Mars was in fact a cold, wet, barren wasteland.
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Curiosity has spent more than a decade in Gale Crater, a Martian landmark where it landed in 2012. The 100-mile-wide crater was formed by an asteroid impact about 3.5 to 3.8 billion years ago. Many signs It was once a lake. Soil samples taken from the crater by Curiosity show some striking characteristics, including being rich in silica and iron but lacking in aluminum.
On Earth, such soils “Serpentinization”the geological processes by which various minerals are transformed SerpentineImportantly, this process requires liquid water, so the presence of material of similar composition in Gale Crater provides further evidence that the crater was once filled with water.
Another important feature of the Martian samples is that they are largely “X-ray amorphous,” meaning that they lack repeating crystal structures that can be examined by X-ray diffraction. The amorphous nature of the samples came as a surprise to scientists, as amorphous materials are generally only considered “metastable.” As the study points out, amorphous materials are “thermodynamically stable and susceptible to transformation into more crystalline mineral phases.”
It’s unclear why this didn’t happen in Gale Crater, but one theory is that the conversion process is inhibited by “kinetic constraints such as low temperatures,” which would suggest that Mars has always been a cold place.
Because it’s impossible to study Martian soil directly, the researchers did the next best thing: They found similar samples on Earth and studied their properties. They looked at several sites with similar soil composition: two in California’s Klamath Mountains, one in western Nevada, and one in Gros Morne National Park in Newfoundland, Canada.
Importantly, the Newfoundland sample was X-ray amorphous, whereas the California and Nevada samples were not. This suggests that Canada’s cold climate was important in preserving the lack of crystalline structure, supporting the theory that something similar may have happened on Mars. [iron]”Gale Crater’s mineral-rich amorphous material is consistent with cool, wet conditions at the time of its formation, followed by cool, dry conditions that favored its persistence.”
“This tells us that there needs to be water there to form these substances.” To tell Anthony Feldman“But to preserve the amorphous material in soil, you need cold conditions, with average annual temperatures close to freezing,” said , a soil scientist and geomorphologist now at DRI and co-author of the study.
The study offers fascinating insights into how scientists can infer information about the environment’s distant past from the geological record, and suggests that the Martian environment was not particularly habitable long ago, even when liquid water flowed on the planet’s cold surface.
