According to a new study, data from NASA’s now-retired InSight mission suggests the presence of a vast underground water reservoir deep beneath the Martian surface.

The research estimates that the water, trapped within tiny cracks and pores in the Martian crust, could be enough to fill hypothetical oceans on the planet. This groundwater could potentially cover Mars with oceans as deep as 1.5 kilometers. The findings were made possible through data gathered by NASA’s InSight lander, which used a seismometer to study Mars’ internal structure from 2018 to 2022.

The study, published in the Proceedings of the National Academy of Sciences, suggests that future astronauts may face significant challenges if they attempt to access this water, as it lies between 11 and 20 kilometers below the planet’s surface. However, the discovery provides critical insights into Mars’ geological history and may offer a new target for the search for life on the Red Planet.

Ancient Martian Water: A Lost Ocean?

Billions of years ago, Mars was likely warmer and wetter, with evidence of ancient lakes, river valleys, and deltas observed by various NASA missions and orbiters. But about three billion years ago, the planet lost its atmosphere, ending its warm and wet period.

Scientists still don’t know why Mars lost its atmosphere, and several missions have been designed to uncover the planet’s water history—where it went and whether it once supported habitable conditions. While some water remains in the form of ice at the poles, researchers believe that this does not account for all of Mars’ “lost” water.

Several theories suggest that the water either evaporated into space, turned into ice, or became locked within minerals or groundwater deep below the surface. New data points to the idea that much of Mars’ water likely seeped deep into the planet’s crust.

Data from InSight: Unlocking Mars’ Secrets

NASA’s InSight mission (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) was a stationary lander that collected unprecedented data about the Martian crust, mantle, core, and atmosphere. Its seismometer recorded Marsquakes—earthquakes on Mars—providing valuable information about the planet’s interior.

Unlike Earth’s tectonic plates, the Martian crust is a single giant plate with cracks and fractures. As Mars continues to cool and contract over time, these cracks cause seismic activity. InSight detected over 1,300 Marsquakes, some occurring thousands of kilometers away from the lander.

The seismic data allowed researchers to study how these quakes travel through the planet, which in turn reveals information about the materials present beneath the surface. By examining the speed of seismic waves, researchers can infer the type of rock, where cracks are located, and what fills these cracks—whether it’s air, minerals, or water.

Using this data, scientists developed a model based on rock physics commonly used on Earth to map underground oil reserves and aquifers. The results showed that the data best matched a layer of volcanic rock deep in Mars’ crust, filled with liquid water.

Water as a Potential Habitat for Life

“The discovery of a massive underground water reservoir opens up possibilities for understanding Mars’ climate history,” said co-author Michael Manga, a professor of Earth and planetary sciences at UC Berkeley. “Water is essential for life as we know it. This underground reservoir could be a habitable environment, just as we find life deep in Earth’s subsurface.”

If Mars’ crust is consistent across the planet, it may hold more water than previously thought—perhaps even more than ancient oceans that may have once existed on the planet’s surface.

While the current analysis doesn’t confirm the existence of life, it suggests that the wet Martian crust could be as hospitable to microorganisms as deep groundwater systems are on Earth. However, accessing such water on Mars would be a major challenge due to the extreme depth. Even drilling a kilometer or more on Earth requires significant energy and infrastructure—tasks that would be even more complex on Mars.

A Puzzle Piece in Mars’ Water History

The discovery of liquid water deep within Mars adds another piece to the puzzle of the planet’s complex water history.

Alberto Fairén, an interdisciplinary planetary scientist and astrobiologist at Cornell University, noted that this finding is the first direct evidence from Mars that confirms the existence of underground liquid water. Fairén, who was not involved in the study, suggested that this water might exist as “a kind of underground sludge.”

“The new findings indicate that liquid water exists deep within the Martian subsurface today, not in isolated lakes but in water-saturated sediments or aquifers,” Fairén said. “Earth’s subsurface biosphere is enormous and contains much of the planet’s microbial diversity and biomass. Some studies even suggest that life on Earth originated deep underground. Therefore, the astrobiological implications of confirming these underground habitats on Mars are incredibly exciting.”

InSight’s Legacy and Future Martian Exploration

While the InSight mission has concluded, its data continues to provide new insights into Mars’ interior. “The results are exactly what I had hoped for from InSight,” said Bruce Banerdt, the mission’s principal investigator. Although Banerdt did not participate in the new study, he acknowledged that the interpretation of the data is robust but still speculative.

Banerdt and lead researcher Vashan Wright both expressed interest in deploying more seismometers on Mars and other planets and moons in the solar system. While InSight’s single seismometer gathered crucial data, placing more instruments across Mars would reveal variations in the planet’s subsurface, offering a more comprehensive view of its complex geological history.

“As on Earth, where groundwater surfaces through rivers and lakes, the groundwater we see today is a record of Mars’ past,” Wright explained.

Conclusion: A New Frontier for Mars Exploration

The discovery of a vast underground water reservoir on Mars not only sheds light on the planet’s ancient climate but also raises exciting possibilities for the search for life. Though accessing this water poses significant challenges, its existence deep beneath the Martian crust offers hope that future missions could explore these aquifers and perhaps even unlock the mysteries of whether Mars ever supported life.

With each new discovery, Mars continues to reveal itself as a dynamic planet with a complex and fascinating history.