Quakes and meteor impacts on Mars produce seismic waves that can be used to explore the planet’s interior. A recent study has examined the seismic waves recorded by the InSight lander and has concluded that there is a significant area located 11-20 kilometers below Mars’ surface, filled with liquid water within cracks and pores. This contradicts previous beliefs about the amount of water that once made up Mars’ surface oceans before they vanished around 3 billion years ago. While this reservoir is too deep for drilling, it could potentially harbor life.
Geophysicists have discovered indications of a vast underground reservoir of liquid water on Mars by analyzing seismic activity—enough to fill oceans on the planet’s surface.
Data acquired from NASA’s InSight lander enabled scientists to estimate that this groundwater could cover Mars to a depth of 1 to 2 kilometers, roughly equivalent to a mile.
While this discovery offers hope regarding the status of water on Mars after its oceans disappeared over 3 billion years ago, access to this reservoir for a future Mars colony is unlikely. It lies within fine cracks and pores in the rock located between 11.5 and 20 kilometers deep within the crust. Even on Earth, drilling to a depth of just one kilometer poses significant challenges.
Nonetheless, this finding highlights another viable location to search for life on Mars, provided the reservoir can be accessed. For now, it contributes insights into the geological history of the planet.
“Understanding the Martian water cycle is essential for comprehending the evolution of its climate, surface, and interior,” stated Vashan Wright, a former postdoctoral fellow at UC Berkeley and currently an assistant professor at UC San Diego’s Scripps Institution of Oceanography. “It’s essential to identify where water exists and how much there is.”
Wright, along with colleagues Michael Manga from UC Berkeley and Matthias Morzfeld from Scripps Oceanography, summarized their analysis in a paper to be published this week in the journal Proceedings of the National Academy of Sciences.
The researchers utilized a mathematical model of rock physics, similar to those used on Earth for mapping underground aquifers and oil fields. They concluded that the seismic information from InSight points towards a deep layer of fractured igneous rock laden with liquid water. Igneous rocks form from the cooling of molten magma, like granite found in the Sierra Nevada.
“The confirmation of a substantial liquid water reservoir gives insights into what Mars may have been like or could still be,” explained Manga, a professor of earth and planetary science at UC Berkeley. “Water is crucial for life as we know it. I don’t see any reason this underground reservoir wouldn’t be capable of hosting life. This is true on Earth—deep mines and the ocean floor host life. While we haven’t found direct evidence of life on Mars, we have identified a location that should theoretically be able to support it.”
Manga was Wright’s postdoctoral mentor, and Morzfeld previously worked as a postdoctoral fellow in UC Berkeley’s mathematics department and is now an associate professor of geophysics at Scripps Oceanography.
Manga emphasized that substantial evidence, such as river channels, deltas, and sediment from lakes, along with water-altered rock, supports the theory that water once flowed across Mars’ surface. However, this wet era ended more than 3 billion years ago when Mars lost its atmosphere. Scientists on Earth have dispatched numerous probes and landers to investigate what happened to that water—much of which cannot be explained by the frozen state observed in the polar ice caps—and to determine when these changes occurred, as well as the potential existence of life on the planet.
The new findings suggest that much of the water did not vanish into space but instead infiltrated the crust.
The InSight lander was launched by NASA to Mars in 2018 to study the crust, mantle, core, and atmosphere, gathering crucial data about the planet’s interior until the mission ended in 2022.
“The mission far exceeded my expectations,” commented Manga. “By analyzing the seismic data collected by InSight, we’ve learned about the crust’s thickness, the depth and composition of the core, and even insights into the mantle’s temperature.”
InSight identified Marsquakes reaching magnitudes of about 5, meteor impacts, and activity from volcanic regions—all of which generated seismic waves that allowed geophysicists to explore the planet’s interior.
An earlier study indicated that above a depth of approximately 5 kilometers, the upper crust likely lacks ice, as Manga and others suspected. This could imply there is minimal accessible frozen groundwater outside of the polar regions.
The recent paper examined the deeper crust and found that the available data is most consistent with the existence of a water-saturated mid-crust below InSight’s position. Assuming the crust’s composition is uniform across the planet, the researchers posited that there could be more water within this mid-crust zone than the volumes believed to have filled theoretical ancient Martian oceans.
This research was supported by the Canadian Institute for Advanced Research, the National Science Foundation, and the U.S. Office of Naval Research.
