The history of water on Mars is a puzzle that is of interest to planetary scientists as well as the general public. The Red Planet currently has water in the form of ice at the poles, trace amounts of gas in the atmosphere, and an unknown amount beneath the surface as ground water, bound in minerals, and in ice. However, there is strong evidence that ancient Mars may have had long-lived streams, rivers, and lakes. There is still much to learn about what Mars was like and how it transformed over time. One approach is to study the inventory of water at different times. Now, NASA’s Perseverance rover has found hydrated magnesium sulfate (similar to Epsom salts) and dehydrated calcium sulfate that were formed by water flowing through cracks in volcanic rocks at the bottom of the 3.8-billion-year-old Jezero crater. These hydrated minerals trap water within themselves and record the history of how and when they formed. Returning samples of these minerals to Earth would allow researchers to explore the history of Mars’ water and climate, and possibly evidence of ancient life with the most sensitive instruments possible.
Jezero crater, Mars. Image credit: NASA / Tim Goudge.
Planetary scientists suspect Mars once had long-lived rivers, lakes and streams.
Today, water on Mars is found in ice at the poles and trapped below the Martian surface.
In new research, University of Cincinnati’s Dr. Andy Czaja and his colleagues revealed that the planet also may have had hydrothermal systems based on the hydrated magnesium sulfate the rover identified in the volcanic rocks.
“When those rocks cool off and fracture, they become a habitable environment for life,” Dr. Czaja said.
“We have not found any definitive evidence of life in these deposits yet. But if there were fossil microorganisms trapped in the rocks, they would be too small to see with the rover.”
“These hydrated minerals trap water within themselves and record the history of how and when they formed.”
“Returning samples of these minerals to Earth would allow researchers to explore the history of Mars’ water and climate and possibly evidence of ancient life with the most sensitive instruments possible.”
Perseverance began its deliberate exploration from the floor of the crater to the front of the delta, formed by an ancient river or drainage channel where it encountered sedimentary rocks that often contain trapped minerals and another avenue for evidence of ancient life.
And last year the rover made it to the crater’s margin in what used to be an enormous lake where it is exploring deposits of magnesium carbonate, which can form geologically or biologically from bacteria.
“The decision to send Perseverance to Jezero crater appears to be paying off,” Dr. Czaja said.
“There were other places we could have gone that might have been just as good.”
“You won’t know until you explore them all. But Jezero was picked for good reason and it has been completely justified.”
Next the rover will make its way out of Jezero crater to explore the wider area.
“We are likely to find rocks dating back 4 billion years or more,” Dr. Czaja said.
“And Mars could harbor stromatolites or rocks that contain evidence of ancient layered mats of bacteria visible to the naked eye.”
“On Earth, these rocks are sometimes found in extreme environments such as geyser basins.”
“I hope that Perseverance has just whetted our appetite for more Martian exploration.”
“And bringing back samples will allow us to study Mars and search for evidence of ancient life with instruments that haven’t even been invented yet for years and years to come.”
The results were published in the January 2024 issue of the Journal of Geophysical Research: Planets.
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Sandra Siljeström et al. Evidence of Sulfate-Rich Fluid Alteration in Jezero Crater Floor, Mars. JGR: Planets 129 (1): e2023JE007989; doi: 10.1029/2023JE00798
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