Researchers have suggested that water on Mars may have enough molecular oxygen to support simple forms of life, according to a study in Nature Geoscience.

Led by Vlada Stamenković from the California Institute of Technology, the scientists modeled the composition of water on Mars, which is thought to exist below the surface as a salty brine.

Doing this, they worked out how much oxygen would be dissolved in the water at various regions on Mars. And they found that almost all locales could support basic aerobic microbial life.

“We find that, on modern Mars… the solubility of oxygen in various fluids can exceed the level required for aerobic respiration,” the team wrote in their paper.

Oxygen is not a key requirement for life on Earth, but it does provide a source of energy. Oxygen on Mars is scarce, however, produced by the breaking down of carbon dioxide caused by sunlight.

The atmosphere of Mars is 160 times thinner than our own, leading many to dismiss the idea it could be oxygenated. But modeling these briny reservoirs, Stamenković and colleagues found that at the expected pressures and temperatures beneath the surface, oxygen could be sufficient for life, and particularly high in the polar regions.

“First, they developed a chemical model describing how oxygen dissolves in salty water at temperatures below the freezing point of water,” a statement from Caltech noted. “Second, they examined the global climate of Mars and how it has changed over the past 20 million years, during which time the tilt of the axis of the planet shifted, altering regional climates.”

The results showed that even though the amounts of oxygen in the Martian atmosphere are very low, these brines could capture enough of it to create a habitat in which microbes would live. They could even hold higher amounts of oxygen than on early Earth more than 2.4 billion years ago.

The findings also seem to be able to explain an unusual feature on Mars, noticeably rocks rich in manganese seen by the Curiosity rover. This manganese would have required significant oxygen to form, and it was thought this may have originated on ancient Mars. But this study suggests a more recent answer.

“It completely changes our understanding of the potential for life on current-day Mars,” Stamenković told National Geographic.

Earlier this year, the European Mars Express spacecraft detected the signal of a vast lake of liquid water beneath the surface of Mars’ south pole. It’s thought that salt could help water like this stay liquid, and survive the sub-zero temperatures on the Red Planet.

And future missions, including NASA’s InSight lander and the Mars 2020 rover, will hopefully tell us more about how habitable Mars was – or is today.