On August 12, US researchers unveiled groundbreaking evidence indicating that Mars may be home to a substantial reservoir of liquid water beneath its surface. Data from NASA’s Mars InSight Lander, which has been monitoring the planet’s seismic activity for the past four years, reveals the presence of significant quantities of water trapped in the Martian crust.

The research, led by Vashan Wright from the University of California San Diego’s Scripps Institution of Oceanography, analyzed seismic waves from over 1,300 Marsquakes recorded by the lander. The findings suggest that these waves traversed through layers of wet rock situated between 11.5 and 20 kilometers (7.1 to 12.4 miles) below the planet’s surface. This discovery stands in contrast to Mars’s arid, desert-like surface and points to a potentially vast underground water reserve.

Karen Lloyd, a subsurface microbiologist at the University of Southern California, called the discovery a “game-changer,” as it opens the door to the possibility of subterranean life on Mars. The notion of Martian life residing underground parallels the concept of Earth’s deep biosphere—a thriving ecosystem of microorganisms living far beneath the Earth’s surface.

For decades, biologists have found evidence of life in extreme underground environments on Earth. Researchers have identified a diverse array of microorganisms living in deep-sea sediments and solid rock formations. These include bacteria and archaea, which have existed for over three billion years and survive in environments cut off from sunlight and nutrients.

The deep biosphere on Earth thrives through chemosynthesis, where microbes derive energy from chemical reactions involving substances like methane and hydrogen sulfide. This life forms a critical part of Earth’s subsurface ecosystem, with estimates suggesting that 70% of all bacteria and archaea live underground.

The potential for similar microbial life on Mars hinges on the presence of water and suitable conditions. While no direct evidence of life has been found on Mars so far, the discovery of substantial water reserves in its crust suggests that the planet’s subsurface may offer conditions conducive to life.

Dr. Cara Magnabosco from ETH Zurich highlights that the same chemosynthetic processes observed in Earth’s deep biosphere could potentially occur on Mars. Although no living organisms have been detected on Mars’s surface, features like ancient canyons indicate that liquid water may have existed on the planet in the past.

This latest discovery by Wright’s team suggests that while the Martian surface may be inhospitable, the subsurface could still harbor microbial life, mirroring the slow-moving, nutrient-scarce ecosystems found deep beneath Earth’s oceans. As researchers continue to explore Mars, these findings may offer new insights into the planet’s potential for hosting life.