An underground reservoir of water may reside beneath the surface of Mars, according to new research released on Monday.

This water, estimated to be located approximately 11.5 to 20 km below the Martian crust, is hidden within cracks in underground rocks. The volume of water present is substantial enough to potentially form a global ocean on Mars.

The findings are based on seismic measurements from NASA's Mars InSight lander, which used a seismometer to detect Mars' interior from 2018 to 2022.

The water on Mars is believed to have transiently existed on the planet's surface over 3 billion years ago when Mars had rivers, lakes, and oceans. This is according to planetary scientist Vashan Wright of the University of California, San Diego's Scripps Institution of Oceanography, who is the lead author of the study published in the journal Proceedings of the National Academy of Sciences.

However, as Mars' atmosphere thinned, it is thought to have lost its surface water. The new findings suggest that the water has seeped into Mars' crust.

"Understanding the Martian water cycle is critical for understanding the evolution of the climate, surface and interior," Wright said.