New research questions long-held principle of the destiny of the Martian waters – Watts with that?
From NASA
Global view of Mars from the Viking orbiter: This global view of Mars is made up of approximately 100 Viking Orbiter images. Credits: NASA / JPL-Caltech / USGS. Download picture>
The new scientific results show that a large amount of the Red Planet’s water is trapped in its crust instead of escaping into space.
Billions of years ago, geological evidence shows that abundant water flowed over Mars and accumulated 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 its water is released into space due to the Red Planet’s low gravity escapes.
Early Mars was believed to have enough water to cover the entire planet in an ocean roughly 100 to 1,500 meters deep – a volume roughly equivalent to half the Earth’s Atlantic Ocean. While some of this water has undeniably disappeared from Mars by atmospheric escape, the new evidence published in the latest issue of Science concludes 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 Caltech Ph.D. presented. Candidate Eva Scheller together with co-author Bethany Ehlmann, Professor of Planetary Sciences at Caltech and Deputy Director of the Keck Institute for Space Studies; Yuk Yung, professor of planetary science at Caltech and senior scientist at NASA’s Jet Propulsion Laboratory; Danica Adams, Caltech PhD student; and Renyu Hu, JPL researcher.
“Atmospheric escape does not fully explain the data we have about how much water actually existed on Mars,” said Scheller.
Using a wealth of cross-mission data archived in NASA’s Planetary Data System (PDS), the research team integrated data from multiple missions of the NASA Mars Exploration Program and from work in the meteorite laboratory. In particular, 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, noting in particular 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 only have one proton in the atomic nucleus, while a tiny proportion (about 0.02%) is in the form of deuterium or so-called “heavy” hydrogen, which has a proton and a neutron. The lighter hydrogen escapes the planet’s gravity into space much more easily than its denser counterpart. Because of this, the loss of a planet’s water through the upper atmosphere would leave an illuminating sign of the ratio of deuterium to hydrogen in the planet’s atmosphere: a very large amount of deuterium would be left behind.
However, the loss of water solely through the atmosphere cannot explain both the observed deuterium-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-hydrogen signal in the Martian atmosphere.
When water interacts with rock, chemical weathering forms clays and other hydrous minerals that contain water as part of their mineral structure. This process takes place on both Earth and Mars. On earth, the old crust continuously melts into the mantle and forms a new crust at the plate boundaries that returns water and other molecules to the atmosphere through volcanism. However, Mars has no tectonic plates, and so the “drying” of the surface, once it occurs, is permanent.
“The hydrated materials on our own planet are continuously being recycled through plate tectonics,” said Michael Meyer, senior scientist for NASA’s Mars Exploration Program at the agency’s Washington headquarters. “Since we have measurements from multiple spacecraft, we can see that Mars is not being recycled and water is now trapped in the crust or has been lost to space.”
A key objective of NASA’s Mars 2020 Perseverance Rover mission to Mars is astrobiology, including finding signs of ancient microbial life. The rover will characterize the geology and past climate of the planet, pave the way for human exploration of the red planet, and be the first mission to collect and cache Martian rocks and regolith (broken rock and dust). Scheller and Ehlmann will support the operation of the Perseverance rover in collecting these samples, which will be returned to Earth via the Mars Sample Return program. This enables the eagerly awaited 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 returned samples, as well as understanding how habitability on rocky planets changes over time.
The research and results outlined in the paper underscore the significant contributions made by young scientists to broadening our understanding of the solar system. Similarly, research, based on data from meteorites, telescopes, satellite observations, and samples analyzed by rovers on Mars, shows the importance of studying the red planet in different ways.
This work was supported by a NASA Habitable Worlds Award, a NASA Earth and Space Science Fellowship Award (NESSF), and a NASA Future Investigator in NASA Earth and Space Science and Technology (FINESST).
HT / OK S.
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