Salty Water Under the Surface of Mars Could Have Enough Oxygen for Life

New models suggest subsurface water could absorb enough oxygen to support microbial communities and even things like sponges

Mars imaged by the Hubble Space Telescope during a close approach to Earth. NASA/Steve Lee/Jim Bell/Mike Wolff

Mars may have a hostile, dusty exterior bathed in dangerous radiation, but a new study suggests that it’s possible life could exist under that inhospitable crust. Pockets of salty water with enough dissolved oxygen to support life may be present in certain parts of the planet, according to a new paper published in the journal Nature Geoscience.

Researchers thought organisms that require oxygen couldn't survive on Mars, since the atmosphere is so thin. Furthermore, water on the Red Planet has only been confirmed in the form of ice or hydrated minerals. So previously, the possibility of salty, oxygen-rich puddles beneath the surface hadn’t been considered.

Using sophisticated computer models, however, the team determined that it is possible for such puddles to exist and potentially support microbes. The planet’s poles—where the temperature is lower and pressure is higher, adding more oxygen to the water—are the most likely place to search for actual evidence of life. In the best-case scenario, the puddles could even have enough oxygen to support more complex organisms, like sponges.

“If there are brines on Mars, then the oxygen would have no choice but to infiltrate them,” co-author Woody Fischer, a geobiologist at Caltech says in a press release. “The oxygen would make it everywhere.”

Maya Wei-Haas at National Geographic reports that the researchers ran the models many times. Even in the worst case scenario, there was still enough oxygen in the water to allow bacterial life to develop.

“We were absolutely flabbergasted,” lead author Vlada Stamenković of NASA's Jet Propulsion Laboratory says. “I went back to recalculate everything like five different times to make sure it's a real thing.”

Mike Wall at reports that Mars has a long, complicated history with water and oxygen. Based on features in the landscape, it’s believed that Mars was once covered with oceans of liquid water billions of years ago. The recently discovered presence of manganese oxide on the Martian surface suggests that not only was the planet wet in the distant past, but it also had plenty of oxygen in its atmosphere. In fact, the early history of Mars suggests it was very similar to Earth.

However, about 4 billion years ago it’s believed a series of solar eruptions stripped away most of the Martian atmosphere, reducing it to about one percent the density of Earth’s. Without that protection, the water evaporated, though there is some evidence that water still exists buried in aquifers and sub-surface pools.

It’s possible that some residual water under the surface has mixed with naturally occurring salts to produce brine. It’s also possible that the miniscule amount of oxygen in the Martian atmosphere is still enough to support life.

“There are so many abiotic ways of creating small but sufficient amounts of oxygen which then, at the colder temperatures, can be absorbed effectively, and could actually maybe trigger evolution in a different way than we got on the Earth,” Stamenković tells Wall at “This is all hypothetical, but worth exploring.”

But the study is just a model, and currently there is no conclusive evidence that these briny puddles—or any liquid water, let alone life of any form—exists on Mars. In the press release, Stamenkovic says the next step in the study is to create some of these hypothetical brines and test whether microbes can indeed live in them. And the step after that is to actually search for these salty reservoirs on Mars.

“Brines are likely to be found in the Martian near-surface, but we haven't had really yet the right instruments, I think, to really answer those questions," Stamenković tells Nicholas Gerbis at radio station KJZZ. To continue the search, he and his team are developing a sensor called TH2OR, which could be used to hunt for water without digging into or disturbing the Martian surface.

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