The new scientific results indicate that a large amount of the Red Planet’s water is trapped in its crust rather than escaping into space.
Millions of years ago, according to geological evidence, abundant water flowed over Mars and collected in pools, lakes and deep oceans. New research funded by NASA shows that a significant amount of its water – between 30 and 99% – is trapped in minerals in the earth’s crust, challenging the current theory that water escaped through space from the Red Planet. .
Early Mars is thought to have enough water to cover the entire planet in an ocean about 100 to 1,500 meters deep – a volume about equal to half of the earth’s Atlantic Ocean. Although some of this water has undeniably disappeared from Mars due to atmospheric escape, the new findings, published in the latest issue of Science, conclude that it is not the bulk of the water loss.
The results were presented at the 52nd Lunar and Planetary Science Conference (LPSC) by lead author and Caltech Ph.D. candidate Eva Scheller with co-authors Bethany Ehlmann, professor of planetary science at Caltech and co-director of the Keck Institute for Space Studies; Yuk Yung, Professor of Planetary Science at Caltech and Senior Research Scientist at NASA’s Jet Propulsion Laboratory; Danica Adams, graduate student at Caltech; and Renyu Hu, JPL researcher.
“Atmospheric escape does not explain the data we have about how much water ever existed on Mars,” Scheller said.
Using a wealth of cross-mission data archived in NASA’s Planetary Data System (PDS), the research team integrated data from several NASA Mars exploration missions and laboratory work. The team specifically studied the amount of water on the Red Planet over time in all its forms (vapor, liquid and ice) and the chemical composition of the current atmosphere and crust of the planet, and especially looked at the ratio of deuterium to hydrogen ( D / H).
While water is made up of hydrogen and oxygen, not all hydrogen atoms are created equal. The vast majority of hydrogen atoms have only one proton in the atomic nucleus, while a small fraction (about 0.02%) exists as deuterium, or so-called ‘heavy’ hydrogen, which has a proton and a neutron. The lighter hydrogen escapes the gravity of the planet much more easily than its denser counterpart. As a result, the loss of water from a planet via the upper atmosphere would leave a sign of the relationship between deuterium and hydrogen in the atmosphere of the planet: there would be a very large amount of deuterium left behind.
However, the loss of water only through the atmosphere cannot explain the observed deuterium-to-hydrogen signal in the Martian atmosphere and large amounts of water in the past. Instead, the study suggests that a combination of two mechanisms – the trapping of water in minerals in the Earth’s crust and the loss of water to the atmosphere – may explain the observed deuterium-to-hydrogen signal within the Martian atmosphere.
When water interacts with rock, chemical weathering forms clay and other hydro minerals that contain water as part of their mineral structure. This process takes place on Earth as well as on Mars. On Earth, old crust constantly melts in the mantle and forms new crust at plate boundaries, which recycles water and other molecules back into the atmosphere through volcanism. Mars, however, has no tectonic plates, and so the ‘drying’ of the surface is permanent.
“The hydrated materials on our own planet are constantly being recycled through plate tectonics,” said Michael Meyer, chief scientist at NASA’s Mars Exploration Program at the agency’s headquarters in Washington. “Because we have measurements from various spacecraft, we can see that Mars is not recovering, and therefore water is now trapped in the crust or lost in space.”
A key objective of NASA’s Mars 2020 Perseverance Rover mission to Mars is astrobiology, including the search for signs of ancient microbial life. The rover will characterize the geology and climate of the planet, pave the way for the exploration of the Red Planet by humans, and be the first mission to collect Mars rock and regolith (broken rock and dust) and place them in the closet. . Scheller and Ehlmann will assist with the operations of the Perseverance Rover to collect these samples that will be returned to Earth by the Mars Sample Return program, enabling the expected further investigation of these hypotheses about the drivers of Mars’ climate change. Understanding the evolution of the Martian environment is an important context for understanding the results of analyzes of the samples returned, as well as understanding how habitability changes over rocky planets over time.
The research and findings outlined in the article highlight the important contributions of scientists in the early career to expand our understanding of the solar system. Similarly, the research, which relied on data from meteorites, telescopes, satellite observations and samples analyzed by robbers on Mars, illustrates the importance of having several ways to explore the Red Planet.
This work was supported by a grant from the NASA Habitable Worlds, a grant from the NASA Earth and Space Science Fellowship (NESSF) and a grant from the NASA Future Investigator in the NASA Award for Earth and Space Science and Technology ( FINESST).
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