Mars likely to have enough oxygen to support life: study

The salt water just below the surface of Mars could contain enough oxygen to support the type of microbial life that emerged and flourished on Earth billions of years ago, researchers reported on Monday. .

In some places, the amount of oxygen available could even keep alive a primitive multicellular animal such as a sponge, they reported in the newspaper. Nature Geosciences.

"We have discovered that brines – water containing high concentrations of salt – on Mars may contain enough oxygen to allow microbes to breathe," said lead author Vlada. Stamenkovic, theoretical physicist at the Jet Propulsion Laboratory in California.

"This completely revolutionizes our understanding of the potential of life on Mars, today and in the past," he told AFP.

Until now, it was assumed that the traces of oxygen on Mars were insufficient to maintain a life, even microbial.

"We never thought that oxygen could play a role in life on Mars because of its scarcity in the atmosphere, about 0.14%," Stamenkovic said.

In comparison, vital gas makes up 21% of the air we breathe.

On Earth, aerobic life forms – that is, breathing oxygen – have evolved with photosynthesis, which converts CO2 into O2. Gas played a crucial role in the emergence of a complex, remarkable life after the so-called "Great Oxygenation Event", about 2.35 billion years ago.

But our planet is also home to microbes – at the bottom of the ocean, in boiling hot springs – that persist in oxygen – deprived environments.

"That's why, every time we thought about life on Mars, we studied the potential for anaerobic life," Stamenkovic said.

Life on Mars?

The new study began with the discovery by NASA 's Mars Curiosity robot of manganese oxides, chemical compounds that can only be produced with a lot of oxygen.

Curiosity, with the orbiter of Mars, has also established the presence of brine deposits, with notable variations in the elements they contain.

A high salt content allows the water to remain liquid – a necessary condition for the dissolution of oxygen – at much lower temperatures, making the brine a place conducive to microbes.

Depending on the region, season and time, temperatures on the red planet can range from minus 195 to 20 degrees Celsius (less than 319 to 68 degrees Fahrenheit).

The researchers have developed a first model describing how oxygen dissolves in salt water at temperatures below zero.

A second model estimated climate change on Mars over the next 20 million years and 10 million years.

Taken together, calculations have shown which areas of the red planet are most likely to produce brine-based oxygen, data that could help determine the location of future probes.

"Oxygen concentrations [on Mars] are orders of magnitude "- several hundred times -" more than necessary by aerobic microbes or breathing oxygen, "concluded the study.

"Our results do not mean that there is life on Mars," warned Stamenkovic. "But they show that Martian livability is affected by the potential for dissolved oxygen."

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More information:
Vlada Stamenković et al. Solubility of O2 in near-surface Martian environments and implications for aerobic life, Nature Geoscience (2018). DOI: 10.1038 / s41561-018-0243-0