Mars, once thought to be a watery world like Earth, may still hold vast reserves of water, but not in the way we imagined. For billions of years, Mars was partially covered in water, evidence of which remains in the form of dry ocean basins and riverbeds on its surface. However, the loss of its magnetic field three billion years ago exposed Mars to the solar wind, causing its atmosphere to dissipate and the water to evaporate into space.
However, a new study published in the Proceedings of the National Academy of Sciences suggests that the water may have been trapped within the pores of volcanic rock, buried 11.5 to 20 km (7 to 13 mi.) underground. This vast reservoir, if brought back to the surface, would cover the entire planet in a mile-deep ocean. Even beneath the surface, the presence of this water could support Martian life within the rocky pores or slurry.
“Water is necessary for life as we know it,” said Michael Manga, study co-author and professor of geophysics and planetary sciences at the University of California, Berkeley, in a . “I don’t see why [the underground reservoir] is not a habitable environment. It’s certainly true on Earth—deep, deep mines host life, the bottom of the ocean hosts life.”
These findings are based on research conducted by the , which landed on Mars in 2018 and operated until 2022. InSight’s seismometer detected marsquakes up to a magnitude of 5— on the Richter scale. While the source of these tremors could be volcanic activity, meteor impacts, or crustal contraction, the speed at which the seismic waves travelled through the subsurface provided crucial information. Computer models of these measurements indicated the presence of a water-saturated region at a depth of 11.5 to 20 km.
“The available data are best explained by a water-saturated mid-crust,” the authors wrote.
The amount of surface water locked in Mars’s polar caps is insufficient to account for the vast amount of water that once existed on the planet, judging by the depth of the river and ocean depressions. This suggests that the water either sank or escaped into space. The new findings point to the former scenario.
“Understanding the Martian water cycle is critical for understanding the evolution of the climate, surface and interior,” said Vashan Wright, another co-author of the paper and an assistant professor of geophysics at the University of California San Diego’s Scripps Institution of Oceanography, in a . “A useful starting point is to identify where water is and how much is there.”
The discovery of this underground water reservoir has significant implications for Martian biology and our understanding of the planet’s history. However, it doesn’t bring us any closer to establishing a Martian colony. The deepest hole ever drilled on Earth, the in northwest Russia, extends about 12 km deep. While this could potentially reach the water on Mars, the logistics of transporting the massive drilling equipment necessary to achieve such a feat to Mars are insurmountable.
“Drilling a hole 10 kilometers deep on Mars—even for [Elon] Musk—would be difficult,” Manga .
