PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.Women's SKECHERS Dark Brown Mary Jane Style Flat Shoes!!! , New Women/Juniors Easy USA Slipon Ballet Flats Bright Yellow Size 9 , womens shoes size 9 Kelly & Katie black flatsWomens Cole Haan Black Suede Air Slip On Clog Mule 11 B , New Cliffs by White Mountain Womens Slip On Shoes Black Flat Sz 6 , stuart weitzman Size 11 Gold Leather Shoes Flats Drivers Embelished , Women's Chinese Ethnic Embroidery Flat Mary Jane Oxford Ballet shoes Solid , Vtg Dr. Martens Oxford Wingtip Shoes 8604 92 Leather Platform Womens UK5 US7 z6PIKOLINOS Brown Leather Slide On Mule Clogs Womens 6 US 36 Flower , Sam Edelman Womens Damian Oxford- Pick SZ/Color.MERRELL Encore Groove Women's 7.5 M Brown Loafer Italian Wool Suede Slip On , Vintage Colorado Womens leather shoes size 9 MWomen's MURTOSA 1502 Beige Leather Mary Janes Shoes SIZE 41 US 10 -Free ShippingFranco Sarto Wedge Heels Iliza Black Pointed Toe Leather Shoes sz 7 , New Steve Madden Black Leather Silver Metal Studded Mule Slip-on Loafer 6 M , Women's HELLE By Romu's Patent Leather Faux-Lizzard Mules Sz. 38 / 5.5 US MINTY!NEW! Hi-Tec Women's Pajo Athletic Shoes Grey/Pink/Lime W5 z , ADIDAS WOMEN'S CF LITE RACER SO W CASUAL RUNNING SHOES (7.5) BLACK/WHITE , K-Swiss Womens Hoke Cmf White/White Fashion Shoes Size 8.5 (356813) , REEBOK Classic Women's White/Blue Sz 7New Balance WX1267BP Women's Cross Training Shoes Size US 9 Running Athletic , Women's Skechers Women's Be-Light-Possibilities Sneaker Elegant And Sturdy Package Athletic Shoes , Women's Women's Altra One Size 8 Linden, Fashion Athletic ShoesNEW CLARKS WOMENS STEP ALLENABAY - WOMENS SPORT SHOES - NAVYNew Balance Women's Classics 993 Running Shoes Navy with Grey Factory Second , CY3 WOMEN'S SHOES 40 HIGH SNEAKERS CYCLE BLUE LEATHER LIST PRICE , Adidas M29685 Climaheat Rocket Boost Winter Running Shoes, Women's US 9.5 , NEW Asics T7H6N 2090 Kanmei Cosmo Pink Black Women's Running Shoes Size 9 , WOMEN'S NIKE FREE 5.0 TR FIT SHOES SIZE US 11 704674001Nike Women's Air Max Team ST size 6.5
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."