PARIS – Salty water just below the surface of Mars could hold enough oxygento support the kind of microbial life that emerged and flourished on Earthbillions of years ago, researchers reported Monday.
In some locations, the amount of oxygen available could even keep alive aprimitive, multicellular animal such as a sponge, they reported in thejournal Nature Geosciences.
“We discovered that brines” – water with high concentrations of salt – “onMars can contain enough oxygen for microbes to breathe,” said lead authorVlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratoryin California.
“This fully revolutionises our understanding of the potential for life onMars, today and in the past,” he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Marswere insufficient to sustain even microbial life.
“We never thought that oxygen could play a role for life on Mars due to itsrarity in the atmosphere, about 0.14 per cent,” Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air webreathe.
On Earth, aerobic – that is, oxygen breathing – life forms evolved togetherwith photosynthesis, which converts CO2 into O2. The gas played a criticalrole in the emergence of complex life, notable after the so-called GreatOxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes – at the bottom of the ocean, inboiling hotsprings – that subsist in environments deprived of oxygen.
“That’s why – whenever we thought of life on Mars – we studied thepotential for anaerobic life,” Stamenkovic.——————————
*Life on Mars?*——————————
Read Top Stories
The new study began with the discovery by NASA’s Curiosity Mars rover ofmanganese oxides, which are chemical compounds that can only be producedwith a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brinedeposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid – a necessarycondition for oxygen to be dissolved – at much lower temperatures, makingbrines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the RedPlanet can vary between minus 195 and 20 degrees Celsius (minus 319 to 68degrees Fahrenheit).
The researchers devised a first model to describe how oxygen dissolves insalty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 millionyears, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet aremost likely to produce brine-based oxygen, data that could help determinethe placement of future probes.
“Oxygen concentrations are orders of magnitude” – several hundred times -“greater than needed by aerobic, or oxygen-breathing – microbes,” the studyconcluded.
“Our results do not imply that there is life on Mars,” Stamenkoviccautioned. “But they show that the Martian habitability is affected by thepotential of dissolved oxygen.” – APP/AFP
