2024-08-16 08:00:00
The data from NASA’s InSight landing module allowed scientists to estimate that the amount of groundwater could cover the entire planet to a depth of between 1 and 2 kilometers.
While this is good news for those tracking the fate of water on the planet after its oceans disappeared more than 3 billion years ago, the reservoir will not be of much use for anyone trying to harness it to supply a future colony on Mars.
Deep waters and possible life within them
The water reservoir is found in small cracks and pores of the rock in the Martian crust, between 11.5 and 20 kilometers below the surface. Even on Earth, drilling a hole one kilometer deep is a challenge.
However, the finding points to another promising location to search for life on Mars, if access to the deposit can be achieved. For now, it helps answer questions about the planet’s geological history.
“Understanding the water cycle on Mars is crucial for understanding the evolution of the climate, both on the surface and inside“, said Vashan Wright, a former postdoctoral fellow at the University of California, Berkeley, now an adjunct professor at the Scripps Institution of Oceanography at the University of California, San Diego. “A useful starting point is identifying where the water is and how much there is“.
Wright, along with colleagues Michael Manga from UC Berkeley and Matthias Morzfeld from Scripps Oceanography, detailed their analysis in a paper published in Proceedings of the National Academy of Sciences (PNAS).
The scientists used a mathematical rock physics model, identical to the models used on Earth to map subterranean aquifers and oil deposits, to conclude that the seismic data from InSight is best explained by a deep layer of fractured igneous rock saturated with liquid water. Igneous rocks are cooled hot magma, like the granite of Sierra Nevada.
“Establishing that there is a large deposit of liquid water allows us to get an idea of what the climate was like or could be“, said Manga, a professor of Earth and Planetary Science at the University of California, Berkeley. “And water is necessary for life as we know it. I don’t see why [the underground deposit] wouldn’t be a habitable environment“.
“It is true that this is the case on Earth: very deep mines harbor life, the ocean floor harbors life. We have not found any evidence of life on Mars, but at least we have identified a place that, in principle, should be capable of harboring life“.
Manga noted that there is plenty of evidence (river channels, deltas, and lake deposits, as well as water-altered rocks) supporting the hypothesis that there once was water on the planet’s surface, but that wet period ended more than 3 billion years ago, after Mars lost its atmosphere.
The new findings indicate that much of the water did not escape into space but rather leaked into the crust.
The InSight landing module was sent by NASA to Mars in 2018 to investigate the crust, mantle, core, and atmosphere, and recorded invaluable information about the interior of Mars before the mission ended in 2022.
InSight detected earthquakes on Mars with a magnitude of 5, meteorite impacts, and rumblings in volcanic regions, all of which produced seismic waves that allowed geophysicists to explore its interior.
A previous article reported that, above a depth of about five kilometers, the upper crust did not contain water ice, as Manga and others suspected. This may mean there is little accessible frozen groundwater outside the polar regions.
The new article analyzed the deeper crust and concluded that “the available data is best explained by a mid-crust saturated with water” beneath InSight’s location. Assuming the crust is similar across the planet, the team argued that there should be more water in this mid-crust area than the “volumes proposed to have filled the hypothetical ancient Martian oceans“.
Reference
Wright, Vashan, Liquid water in the Martian mid-crust, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2409983121.