By utilizing seismic activity to explore the interior of Mars, geophysicists have uncovered compelling evidence of a substantial underground reservoir of liquid water with the capacity to fill the planet’s former oceans. NASA’s Insight lander provided the crucial data that enabled scientists to estimate the size of the groundwater, suggesting that it could envelop the entire planet at a depth ranging from 1 to 2 kilometers or about a mile.
Although this discovery presents fascinating implications for understanding the history of water on Mars following the disappearance of its oceans over 3 billion years ago, it may not be immediately beneficial for potential human settlement on the planet.
The reservoir is located in narrow crevices and pores in the Martian crust, existing between 11.5 and 20 kilometers (7 to 13 miles) below the surface, posing significant challenges for potential extraction. Nonetheless, the presence of this vast reservoir provides an intriguing possibility for the search for life on Mars, contingent on the ability to access it.
Overall, this remarkable finding not only sheds light on the geological evolution of Mars but also offers a potential pathway for uncovering new opportunities and resources on the red planet.
“Understanding the Martian water cycle is critical for understanding the evolution of the climate, surface, and interior,” said Vashan Wright, a former UC Berkeley postdoctoral fellow who is now an assistant professor at UC San Diego’s Scripps Institution of Oceanography. “A useful starting point is to identify where water is and how much is there.”
Wright, alongside colleagues Michael Manga of UC Berkeley and Matthias Morzfeld of Scripps Oceanography, detailed their analysis in a paper.
The analysis utilized a rock physics model commonly employed on Earth to map underground aquifers and oil fields. Based on the seismic data from Insight, it was determined that a deep layer of fractured igneous rock saturated with liquid water best explains the observations. Igneous rocks, such as the granite in the Sierra Nevada, are formed from cooled magma.
“Establishing that there is a big reservoir of liquid water provides some window into what the climate was like or could be like,” said Manga, a UC Berkeley professor of Earth and planetary science. “And water is necessary for life as we know it. I don’t see why [the underground reservoir] is not a habitable environment. It’s certainly true on Earth — deep, deep mines host life, and the bottom of the ocean hosts life. We haven’t found any evidence for life on Mars, but at least we have identified a place that should, in principle, be able to sustain life.”
Manga pointed out compelling evidence suggesting that water once flowed on Mars’ surface, supported by the presence of river channels, deltas, and lake deposits. This wet period ended over 3 billion years ago after Mars lost its atmosphere. Scientists are keen on uncovering what happened to the water, when it occurred, and whether life once thrived on the planet. Recent findings suggest that a significant portion of the water did not escape into space but rather seeped into the crust.
To investigate further, NASA’s Insight lander was deployed to Mars in 2018 to explore the planet’s crust, mantle, core, and atmosphere. The mission yielded valuable insights into Mars’ interior before concluding in 2022.
“The mission greatly exceeded my expectations,” Manga said. “From looking at all the seismic data that Insight collected, they’ve figured out the thickness of the crust, the depth of the core, the composition of the core, even a little bit about the temperature within the mantle.”
Insight has successfully detected Mars quakes of up to about a magnitude of 5, meteor impacts, and rumblings from volcanic areas. Geophysicists have been able to probe the planet’s interior by studying the seismic waves produced by these events.
A previous study suggested that the upper crust of Mars, at a depth of about 5 kilometers, does not contain water ice as previously suspected by some researchers. This finding may indicate that there is little accessible frozen groundwater outside of the polar regions.
The new paper analyzed the deeper crust and concluded that the “available data are best explained by a water-saturated mid-crust” below Insight’s location. Assuming the crust is similar throughout the planet, the team argued, there should be more water in this mid-crust zone than the “volumes proposed to have filled hypothesized ancient Martian oceans.”
Journal reference:
- Vashan Wright, Matthias Morzfeld, and Michael Manga. Liquid water in the Martian mid-crust. Proceedings of the National Academy of Sciences, 2024; DOI: 10.1073/pnas.2409983121