Hidden reservoir: There may be a massive reservoir of liquid water seven miles beneath the Martian surface — enough to flood the entirety of Mars to a height of one to two kilometers, data from NASA’s Mars InSight probe suggests. The water is hidden in cracks and pores in fractured crustal rock and may have originated in Mars’ ancient ocean. While it won’t be accessible to future Mars astronauts, it’s theoretically conceivable that Martian life could still be hidden there, the team reports.
Mars is dry and cold today, but until three billion years ago there were still rivers, lakes and even a flat, great ocean. But climate change has ended this era of life on the Red Planet and the waters have disappeared. But where to? Data from Mars probes suggest that Mars’ polar ice caps are not large enough to store all the water from the ancient ocean. Also those in the mid-latitudes beneath the surface of Mars Water ice deposits are not enough for this.
But where did the water in the Martian ocean go? Until now, most planetary scientists assume that Mars has a large part of its water lost in space: Due to the lack of a magnetic field, the solar wind was able to tear off parts of the Martian atmosphere and with it water into space.
Detection of water in the middle crust of Mars
But there is another possibility, as Vashan Wright of the University of California, San Diego, and his colleagues have discovered. They wanted to know if Martian ocean water could be hidden deep within the Martian crust. To do this, they evaluated earthquake data recorded by the seismometer on NASA’s Mars InSight lander. These seismological data have already revealed that there are depths of about 300 meters at the Mars InSight site. almost no water in the Martian crust.
However, Wright and his colleagues have now taken their research further. They focused on Mars’ middle crust, at a depth of 11.5 to 20 kilometers. “Temperatures on Mars today are warm enough to support stable liquid water on top of the middle crust,” the researchers explain. Previous analyses had also shown that this area of the crust could be riddled with abundant rocky pores.
For their study, the scientists specifically analyzed seismic data that provide information on the nature of the middle crust of Mars. To do this, they used a mathematical model of rock physics used on Earth to locate oil deposits and underground water reservoirs.
Huge reservoir filled with interstitial water
And indeed: the analyses confirmed, on the one hand, that the average crust of Mars is porous – the cavities therefore make up about 17% of the rock. On the other hand, the seismic data suggest that the fine cracks and pores in the rock are filled with liquid water. “A fractured average crust of igneous rock saturated with liquid water best explains the existing data,” Wright and his colleagues write.
But it does mean that there could be a huge reservoir of liquid water deep beneath the surface of Mars – provided that the results are representative not only of the Mars probe’s location, but also of the rest of the planet. Mars could then have a planet-wide repository of deep groundwater, stored in the pores of rocks.
Enough for an entire ocean
According to the researchers’ calculations, there could be enough water in the middle crust of Mars for a global ocean – the water could flood the entire surface of Mars with water from a height of one to two kilometers. The deep reservoir of pore water could also explain where the water of the ancient Martian ocean disappeared: “Mars must therefore not have lost its water due to atmospheric outgassing,” the team writes.
Instead, much of the ancient Martian ocean could have seeped into the depths of the Martian crust – and then remained as pore water to this day. This deep water reservoir would not be usable for future astronauts and Mars stations on Mars, because no drilling technology can reach that depth. Nevertheless, the existence of such an aquifer on Mars is potentially significant, the scientists explain.
A refuge for Martian life?
“Knowing that there is a large reservoir of liquid water gives us a window into the past climate of Mars,” says Michael Manga, a co-author of the study from the University of California, Berkeley. At the same time, the deep reservoir represents a place where there could be life on Mars. Because on Earth, there are microbes even miles deep in crustal rocks. This Deep biosphere thrives despite constant darkness and lack of oxygen.
The situation could be similar on Mars, the researchers say: “Since water is a prerequisite for life as we know it, I don’t see why the subsurface reservoir on Mars shouldn’t be a suitable environment for life,” Manga says. “Although we haven’t yet found any evidence of life on Mars, we now have at least one place that, in principle, would support life.” (Proceedings of the National Academy of Sciences, 2024; is that i: 10.1073/pnas.2409983121)
Source: University of California – Berkeley, University of California – San Diego
August 13, 2024 – Nadja Podbregar