New Study Challenges Long-Standing Theory of the Fate of Mars Water – NASA Mars Exploration Program

The new scientific results indicate that a large amount of the Red Planet’s water is trapped in its crust rather than having escaped into space.

Billions of years ago, according to geological evidence, abundant water flowed through Mars and accumulated in pools, lakes, and deep oceans. New research funded by NASA shows that a substantial amount of its water, between 30 and 99%, is trapped within minerals in the planet’s crust, challenging the current theory that due to the low gravity of the red planet, its water escaped into space.

The first Mars was thought to have enough water to have covered the entire planet in an ocean roughly 100 to 1,500 meters (330 to 4,920 feet) deep, a volume roughly equivalent to half of Earth’s Atlantic Ocean. While it is undeniable that some of this water disappeared from Mars through atmospheric escape, the new findings, published in the latest issue of Science, conclude that it does not explain most of its water loss.

The results were presented at the 52nd Lunar and Planetary Science Conference (LPSC) by lead author and Ph.D. from Caltech. candidate Eva Scheller along with co-authors Bethany Ehlmann, professor of planetary science at Caltech and associate director of the Keck Institute for Space Studies; Yuk Yung, professor of planetary science at Caltech and principal research scientist at NASA’s Jet Propulsion Laboratory; Danica Adams, Caltech graduate student; and Renyu Hu, a research scientist at JPL.

“Atmospheric leakage does not fully explain the data we have on how much water actually existed on Mars,” Scheller said.

Using a large amount of cross-mission data archived in NASA’s Planetary Data System (PDS), the research team integrated data from multiple missions from NASA’s Mars Exploration Program and meteorite laboratory work. Specifically, the team 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 planet’s current atmosphere and crust, looking in particular at the proportion of deuterium. to hydrogen (D / H).

Although water is made up of hydrogen and oxygen, not all hydrogen atoms are the same. The vast majority of hydrogen atoms have only one proton within the atomic nucleus, while a small fraction (about 0.02%) exists as deuterium, or so-called “heavy” hydrogen, which has one proton and one neutron. Hydrogen, which is lighter, escapes the planet’s gravity into space much more easily than its denser counterpart. Because of this, the loss of water from a planet through the upper atmosphere would leave a telltale sign about the ratio of deuterium to hydrogen in the planet’s atmosphere: a large amount of deuterium would remain.

However, the loss of water solely through the atmosphere cannot explain as much the signal from deuterium to hydrogen observed in the Martian atmosphere as the large amounts of water in the past. Instead, the study proposes that a combination of two mechanisms, the retention of water in minerals in the planet’s crust and the loss of water to the atmosphere, may explain the deuterium-to-hydrogen signal observed within the Martian atmosphere.

When water interacts with rock, chemical weathering forms clays and other hydrated minerals that contain water as part of their mineral structure. This process occurs both on Earth and on Mars. On Earth, the old crust continually melts into the mantle and forms a new crust at the plate boundaries, recycling water and other molecules into the atmosphere through volcanism. Mars, however, does not have plate tectonics, so the “drying” of the surface, once it occurs, is permanent.

“Hydrated materials on our own planet are continually recycled through plate tectonics,” said Michael Meyer, senior scientist for 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 being recycled, so the water is now locked up in the crust or lost to space.”

A key objective of NASA’s Perseverance Mars 2020 rover mission to Mars is astrobiology, including searching for signs of ancient microbial life. The rover will characterize the planet’s geology and past climate, pave the way for human exploration of the Red Planet, and be the first mission to collect and store Martian rocks and regoliths (broken rocks and dust). Scheller and Ehlmann will assist in the Perseverance rover operations to collect these samples which will be returned to Earth through the Mars Sample Return program, allowing for the much anticipated further examination 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 the analyzes of the returned samples, as well as understanding how habitability changes over time on rocky planets.

The research and findings described in the paper highlight the significant contributions of early career scientists to expanding our understanding of the solar system. Similarly, the research, which drew on data from meteorites, telescopes, satellite observations, and samples analyzed by rovers on Mars, illustrates the importance of having multiple ways to probe the Red Planet.

This work was supported by a NASA Habitable Worlds Award, a NASA Earth and Space Science Fellowship (NESSF) Award, and a NASA Future Investigator in NASA Earth and Space Science and Technology (FINESST) Award.

News media contacts

Gray Hautaluoma / Alana Johnson
NASA Headquarters, Washington
202-358-0668 / 202-358-1501
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Good Andrew
Jet Propulsion Laboratory, Pasadena, California.
[email protected]


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