New seismic data from NASA’s InSight lander suggests that liquid water may still exist beneath the Martian surface, a promising development for future human exploration and settlement.
An international team of researchers from China, Australia, and Italy collaborated on the new study, which utilized NASA’s InSight seismometer data to probe the Martian interior with unprecedented resolution.
Between Mars’ initial formation and roughly 3 billion years ago, the planet held a significant amount of surface water. Geological evidence from the early Noachian and Hesperian periods indicates that Mars was once covered in lakes, rivers, and even oceans. However, during the Amazonian period, much of that water vanished from the surface, leaving behind the cold, dry landscape we see today. One possibility is that the water dissipated into space under the force of strong solar winds—but that’s not the only explanation.
Just because water is no longer visible on the surface doesn’t mean it’s absent from the planet. Whether—and how deeply—liquid water might still exist within Mars’ crust remains a central question for planetary scientists. Earlier studies had suggested that the middle crust could contain some water, but its quantity and distribution remained unclear. Locating a local water source would be a major breakthrough for future crewed missions and potential long-term settlements.
“The water involves profound questions about life and humanity’s future on the Red Planet,” said co-author Dr. Hrvoje Tkalčić of The Australian National University.
Probing Mars’ Seismic Events
Launched in May 2018, NASA’s InSight lander touched down on Mars in November of that year. Of its three instruments, the Seismic Experiment for Interior Structure (SEIS) returned a steady stream of data until the mission concluded in December 2022. During those four years, SEIS recorded numerous seismic events, but the team focused on three in particular: S1000a and S1094b, the two largest meteor impacts detected, and S1222a, the largest marsquake observed during the mission.
The strength of these events allowed researchers to achieve deeper vertical resolution of the Martian crust than ever before. The team used two independent inversion techniques to ensure a robust interpretation of the data. Ultimately, their improved model revealed three distinct crustal layers, compared to the single-layer structure seen in earlier studies.
Water Beneath the Surface Revealed
By analyzing the seismic waveforms, the researchers identified a low shear-wave velocity anomaly located 5.4 to 8 kilometers below the surface—an indicator consistent with the presence of subsurface water. From this anomaly, they estimate that Mars could contain a global equivalent layer (GEL) of water ranging from 520 to 780 meters thick. This is in contrast to ancient Mars, which is believed to have supported a GEL as deep as 1,500 meters.
The team believes the water likely remains in liquid form, with temperatures at that depth estimated to be above freezing. Meanwhile, the surface remains so cold that any water within the top 5 kilometers is likely frozen solid.
However, the findings come with important caveats. The estimate is based on a single local reading from the SEIS instrument and doesn’t account for lateral structural variations across Mars. Additionally, the model does not include primordial water that may still be present deeper within the crust. Further studies will be required to develop a more complete understanding of Mars’ hidden water reserves.
The paper “Seismic Evidence of Liquid Water at the Base of Mars’ Upper Crust” appeared on April 25, 2025 in National Science Review.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.