Scientists have discovered compelling evidence of a vast underground ocean beneath the Martian surface, potentially containing enough water to cover the entire planet in a sea up to two kilometres deep, according to groundbreaking analysis of seismic data from NASA’s InSight lander.
The revelation, published in the Proceedings of the National Academy of Sciences in August 2024, suggests that Mars’ missing water did not entirely escape into space as previously thought, but instead retreated deep underground where it has remained locked away for billions of years. The discovery fundamentally reshapes our understanding of Mars’ geological history and significantly boosts the possibility that microbial life could exist on the Red Planet today.
Using data from more than 1,300 Marsquakes recorded between 2018 and 2022, researchers identified a “low-velocity layer” between 11.5 and 20 kilometres beneath the surface, where seismic waves slowed dramatically. This anomaly indicates fractured igneous rock saturated with liquid water, creating what scientists describe as a massive, planet-wide aquifer system.
“Establishing that there is a big reservoir of liquid water provides some window into what the climate was like or could be like,” said Professor Michael Manga from the University of California, Berkeley, who co-authored the study. “And water is necessary for life as we know it. I don’t see why the underground reservoir is not a habitable environment.”
Revolutionary Seismic Detection Method
The InSight mission, which operated from November 2018 until December 2022, deployed sophisticated seismometers to listen to Mars’ internal rumblings. These instruments detected Marsquakes up to magnitude 5, meteor impacts, and volcanic tremors, all producing seismic waves that behaved differently depending on the materials they passed through.
Dr Vashan Wright, lead author and geophysicist at the University of California San Diego’s Scripps Institution of Oceanography, explained that the team employed mathematical models identical to those used on Earth to map underground aquifers and oil fields. “Understanding the Martian water cycle is critical for understanding the evolution of the climate, surface and interior,” Wright stated.
The seismic data revealed that whilst the top five kilometres of Martian crust appear dry, the mid-crust zone contains water-filled fractures and pores. If InSight’s location at Elysium Planitia near Mars’ equator is representative of the entire planet, the underground water could fill a global ocean between one and two kilometres deep.
Japanese researchers from Hiroshima University provided supporting evidence in March 2025, performing tests on diabase rocks from Sweden that closely resemble Martian rocks. When saturated with water, these Earth analogues produced similar seismic signatures to those detected by InSight’s SEIS instrument.
Profound Implications for Martian Life
The discovery dramatically enhances the possibility of present-day microbial life on Mars. On Earth, similar deep subsurface environments teem with life, including locations like Canada’s Kidd Creek Mine, where “sulfate-reducing” microbes thrive more than a mile underground in water that hasn’t seen daylight for over a billion years.
“It’s certainly true on Earth, deep, deep mines host life, the bottom of the ocean hosts life,” Manga noted. “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.”
Research published in 2021 by Brown University scientists found that Martian meteorites contain all the necessary ingredients for radiolysis-driven habitats. This process, where radioactive decay breaks down water molecules to produce chemical energy, could support microbial communities similar to those surviving in Earth’s unlit depths.
Dr Jesse Tarnas, who led that study, stated: “The big implication here for subsurface exploration science is that wherever you have groundwater on Mars, there’s a good chance that you have enough chemical energy to support subsurface microbial life.
Rewriting Mars’ Hydrological History
The underground ocean discovery solves a long-standing mystery about Mars‘ “missing water.” Evidence from ancient river valleys, lake beds, and sedimentary deposits has long suggested Mars was once a warmer, wetter world with surface water. However, after the planet lost its atmosphere more than three billion years ago, scientists assumed most water either froze at the poles or escaped into space.
This new finding indicates a third possibility: much of Mars’ ancient surface water seeped underground, becoming trapped in the planet’s porous rock layers. The water likely remains liquid due to pressure from overlying rock and potentially mineral interactions that lower its freezing point.
Supporting evidence emerged in February 2025 when Chinese scientists analysing data from the Zhurong rover reported finding ancient beach deposits, suggesting Mars once had ice-free oceans during a period when the planet maintained a denser atmosphere capable of retaining heat.
Challenging Access, Promising Future
Despite the monumental discovery, accessing this water presents extraordinary challenges. At depths of 11.5 to 20 kilometres, the reservoir lies far beyond current drilling capabilities, even on Earth. The deepest human drilling project, Russia’s Kola Superdeep Borehole, reached only 12.3 kilometres after decades of work.
“It would be very challenging,” acknowledged Wright. “Only a few projects have ever bored so deep into Earth’s crust, and each one was an intensive undertaking. Replicating that effort on another planet would take lots of infrastructure.”
Bruce Banerdt, InSight’s principal investigator, expressed satisfaction with the mission’s achievements: “The mission greatly exceeded my expectations. 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.”
Revolutionary Understanding of Habitability
The discovery has prompted scientists to expand their concept of habitable zones beyond traditional surface environments. Research published in July 2025 by New York University Abu Dhabi introduced the concept of a “radiolytic habitable zone,” where cosmic rays penetrating underground could provide energy for microbial metabolism through water radiolysis.
Dr Dimitra Atri, who led that study, explained: “This research opens up exciting new possibilities in the search for life beyond Earth and suggests that even the darkest, coldest places in the Solar System could have the right conditions for life to survive.”
Emil Ruff from the Marine Biological Laboratory, whose December 2024 research compared Earth’s subsurface microbiomes, noted striking parallels: “Three kilometres beneath the surface of Earth and Mars look very similar, so understanding Earth’s subsurface life will provide clues what to look for on other celestial bodies.
Transforming Future Mars Exploration
The underground ocean’s existence fundamentally alters strategies for future Mars missions. NASA’s Perseverance rover, currently exploring Jezero Crater, and the European Space Agency’s upcoming ExoMars mission focus primarily on surface exploration. However, these new findings suggest that accessing the deep subsurface should become a priority for astrobiology.
“If we want to think about the possibility of present-day life, the subsurface is absolutely going to be where the action is,” emphasised Professor Jack Mustard from Brown University.
The discovery also holds implications for future human colonisation efforts. Whilst the deep reservoir remains inaccessible with current technology, confirming abundant water locked within Mars’ crust suggests other, shallower water sources may exist that could support human settlements.
Scientific Consensus Building
The scientific community has broadly embraced the findings, though some researchers urge caution. Banerdt, whilst impressed by the analysis, noted that interpretations of seismic data can be “somewhat speculative” and that “there is almost always another way to explain any given set of data.”
Nevertheless, the convergence of evidence from multiple sources, including seismic data, meteorite analysis, rover observations, and laboratory experiments on Earth analogues, builds a compelling case for the underground ocean’s existence.
As humanity continues its quest to answer whether we are alone in the universe, this hidden Martian ocean represents one of the most promising environments for extraterrestrial life in our solar system. Though currently beyond our reach, it offers tantalising possibilities for future generations of explorers and scientists determined to unlock Mars’ deepest secrets.
The discovery proves that Mars, far from being a dead world, remains geologically and potentially biologically active, harbouring vast reservoirs of water that could sustain life in its hidden depths.
Follow for more updates on Britannia Daily
