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.Dimmi Footwear Adventure Women's Shoes Sz 6 1/2 6.5 Color Red Charcoal Cinnamon , Women's Wear Ever Mule Shoes - 6M , SELBY WOMENS BROWN WOVEN LEATHER LOAFERS SIZE 6.5 AA NARROW USVidoreta Womens Serafina Sequin Round Toe Casual Espadrilles Flats BHFO 7749NAOT Attitude Taupe/Nubuck Leather Mary Jane Women's Shoes 7Tommy Hilfiger Womens Red Mesh Slip On Clog Chunky Mule Size 8 M W20548 , Dunham Hemlock Slip On Casual Shoe, #WCE910, Brown, Leather, Women's US 7.5ECCO Women's Leathe Shock Point Mocassin Loafer Size 9-9.5Explore24 easyspin woman's size 8.5-9 slip on sandalsASICS GT 2000 T550N Running Training Shoes Womens Size 7 Gray Purple Aqua , BIRKENSTOCK MULES Mules Slippers Home Slippers Black 051791 NewRyka Womens Brown Casual Walking Shoes Size 9Minnetonka Women's Hello Kitty Kilty MocNew Women's Skechers Empire Inside Look Slip On Casual Shoes 12419 Gry/Wht dc 0RMadden Girl Womens kudos Low Top Zipper Fashion Sneakers, Black/Star, Size 7.0 tColumbia Drainmaker II Womens 9 Techlite Athletic Running Water Shoes Y601 , adidas Lite Racer Running Shoes-Women's size 11 Black , Women's ROMANCE-301-2 Quality Products Athletic ShoesNike Mercurial Victory VI Dynamic Fit FG Womens Size 7 Soccer Cleats AJ7650 991 , Reebok Women's CL Nylon Neutrals Sneaker - Choose SZ/ColorFabulicious Women's Belle 301F Red SatinWMNS NIKE FREE TR MTLC. Size: 7.5. Dark Grey/Metallic Silver Model: 849805001New Womens Nike SF AF1 MID Special Forces Shoes Air Force 1 AA3966-002 sz 7.5Skechers Women's Go Walk Lite-Luna Boat ShoeNew Balance W1260GG6 Athletic Shoes - Women's Size 7 B, Turquoise/Teal , Women's ADIDAS Pink Supernova Geofit Sequence 6 Athletic Shoes Size 10.5M , Reebok Crossfit One Cushion 3.0 (Size 8,9, 9.5, 10)Ryka Aries Walking Fitness Athletic Shoes Sneakers Womens MULT COLORS + SIZES , Puma Roma NBK Patent Geranium/Gray Violet Women's 359298 03 SZ 7.5New Fila Cool Max Fresh 3 Black Turquoise Running Women's Shoes SIZE 6
"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."