Martian saltwater could have enough oxygen to support life

A new study suggests that salt water buried just below the Martian surface could contain enough dissolved oxygen to support microbes, or even a simple animal life such as sponges in some places.

This surprising finding could help reshape scientists' understanding of the past and present livability of the red planet, study team members said.

"We live in an exciting time," said lead author Vlada Stamenković, a research scientist at NASA's Jet Propulsion Laboratory in Pasadena, California. "Especially since there is still a lot of work to be done to better understand the Martian livability, I hope that it creates excitement in the [scientific] the community, in the world, to think of Mars as a potential place for life maybe even today. " [The Search for Life on Mars (A Photo Timeline)]

Underground water

The water flowed generously over the red earth of Mars in the past, as have shown spacecraft such as NASA's Viking orbiters, Mars Reconnaissance Orbiter and the Curiosity, Spirit and Opportunity rovers. Indeed, many scientists believe that the red planet even represented the oceans billions of years ago.

This surface water has long since disappeared, after Mars lost most of its atmosphere and passed into the cold, dry world we know today. But researchers believe that some wet matter probably still exists underground – in deep-buried aquifers and pockets of salt brine, some of which may be just below the surface.

For example, some scientists believe that Martian seasonal black streaks, called recurrent slope lines, are caused by the leaking of such brines, which can remain liquid at much lower temperatures than "pure" water because of their salt content.

Stamenković and his colleagues modeled the oxygen retention potential of brine tanks located near the surface, calculating the amount of dissolved O2 that they could contain at various locations around the Martian globe.

It is an interesting astrobiological question. Life as we know it does not necessarily need oxygen; After all, the Earth's early organisms were anaerobic, just like a huge part of the modern microbial diversity of the planet. But oxygen is a source of energy so rich that its availability allows for many interesting pathways of evolution, such as the rise of complex life of plants and animals. (Almost all known multicellular species on Earth breathe oxygen one way or another.)

The researchers found that Martian brines could contain a lot of oxygen – enough to support aerobic microbial life everywhere, if the requirements of these hypothetical Mars bugs were similar to those of the Earth. And the models have shown that the dissolved oxygen capacity varies considerably over time and from one place to another, because it depends on the temperature and, to a lesser extent, the pressure. (The temporal variation is related to the displacements of the skew of Mars – the inclination of its axis of rotation.)

Colder temperatures promote greater oxygen input into brines. Thus, researchers have determined that the ice pockets near the Martian poles could be oxygen rich enough to accommodate complex multicellular organisms such as sponges. Such "aerobic oases" may be common nowadays above 67.5 degrees north latitude and below 72.5 degrees south latitude. [Photos: The Search for Water on Mars]

Astrobiologists should not make fun of extremely cold environments just because relatively warm environments tend to be better for life, as we know on Earth, Stamenković said.

"Every environment has its advantages and disadvantages," he told Space.com.

Stimulate research

According to the members of the study, there is evidence of observation to support the new modeling results. For example, the Curiosity rover spotted manganese oxides during its exploration of the 96-km wide Gale crater on Mars.

It takes a lot of dissolved oxygen to produce these minerals, Stamenković said. Here on Earth, he added, manganese oxides only formed when O2 began to persist in the atmosphere, about 2.5 billion years ago. – a milestone known as the "Great Oxygenation Event" (GOE).

"Our model says that [manganese oxide formation] is possible to occur on Mars, because of the brackish environment and low temperatures, "Stamenković said.

The GOE was linked to the rise of oxygenic photosynthesis, which today produces almost all of the oxygen in the Earth 's air. The air of Mars contains only a small amount of oxygen produced in an abiotic way, but that does not mean that any of these elements can not make buried brines. For example, in addition to traces of atmospheric oxygen, radiation emitted by radioactive elements in Martian rocks could split water molecules into the hydrogen and oxygen that compose them, Stamenković said.

Indeed, radiolysis and / or other processes may have played an important role in almost the entire history of the red planet. So it is possible that life on Mars – if it ever happens – has access to energy-rich oxygen for billions of years. And so are other worlds with cold and habitable environments, such as the buried moons of the ocean, Europa and Enceladus (which respectively orbit Jupiter and Saturn), Stamenković said.

"There are so many abiotic ways to create small amounts of sufficient oxygen that, at cooler temperatures, can be absorbed effectively and could even trigger a different evolution than we had on Earth," he said. he declared. "All of this is hypothetical, but deserves to be explored."

NASA and the European Space Agency (in partnership with Russia) aim to launch rovers in search of life to Mars in 2020. But these two robots will look for traces of their past lives. The last and until now the only spacecraft to search the current Red Planet organisms on the Martian surface was NASA's twin Viking 1 and Viking 2 landing gear, which landed in 1976.

Stamenković wants this to change, and he hopes the new study – which was published online today (October 22) in the journal Nature Geoscience – will provide a small boost in this direction.

"There is still so much about Martian livability that we do not understand, and it is high time to send another mission that tackles the issue of groundwater and potential life on Mars and look for these signals, "he said.

Mike Wall's book on the search for extraterrestrial life, "Over there" will be published on November 13 by Grand Central Publishing. Follow him on Twitter @michaeldwall. follow us @Spacedotcom or Facebook. Originally published on Space.com.