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.Nine West Beachinit Flat Espadrilles, Black Multi, 9 US DisplayWomen Ladies Summer moccasins with American symbols, Size 11 US, Euro 42 , Eastland Womens gia Leather Almond Toe Ballet FlatsBlack Patent Leather Pointy Toe Buckle Studs Strappy Straps Flats Ballerina Shoe , SC35 Audreyy Wrap Bow Ballet Flats 676, Dark Natural, 6 US , Crocs Women’s Brown Clogs Mary Jane Shoes Ankle Straps Slip-On Size 9Sacha London Wilma Size 6 7 8 Woven Yellow Blue Dress Casual BalletFlat Shoe New , Betsey Johnson Rose Gold Marilyn Face Embellished Beaded Ballet Flats Sz 6Women’s SAS Tripad Size 6 Wide Shoe Comfort Black Faux Snake Skin Moc Toe Loafer , Sperry Top Sider Women Bluefish 2 Eye Boat Shoes Leather Size 7.5 M 9276619 , Cole Haan Womens Size 8.5 B Waterproof Black Suede Zip Mules Shoes EUC , NEW SALA EUROPE ERINE WOMENS COMFORT PEEP TOE LEATHER SHOESSAS TRIPAD Women's Navy Blue Slip On Leather Moc Toe Loafers Sz 9 N , 629 NEW Ron White Winley Dove Suede Perforated Derby Women's Sz 37.5 M , Stuart Weitzman Womens 7.5 M brown snakeskin ballet flat shoes gold buckle pumpsEcco Black Leather Mary Janes Womens Size 37 , Dirty Laundry Chinese Laundry Women's Fur Ever Fashion Sneaker, White Leather, 1 , Jack Rogers Reese Suede Flat NEW Anchor , REEBOK Running DMX Foam RbX Womens Athletic Shoes Sneakers White & Blue Size 9Women's FILA Blue MEMORY SPEEDSTRIDE Athletic Running Casual Shoes 5RM00022 NEWShop6 2018 Fashion Couples Breathable Sport Sneakers Running Flats Canvas Shoes , Heelys Propel 2.0 Skate Shoes - Women's Size 8, Grey/Pink 1014Women's VICTORIA Toile 106613 Noir Blanc The King Of Quantity Athletic Shoes , Puma Roma Hyper SL NBK 2 Infrared Black White Womens Sneakers 357995-01 1703-59 , VANS Sk8 Hi Slim Gossamer Green/Blanc de Blanc Skate Shoes WOMEN'S Size 9.5 , Adidas Lite Speedster 3 Women's Running Shoes Fitness Gym Trainers NavyChampion US Shoe Size Women Runner Comfort Casual Athletic Sneakers Black White , VTG USA L.L. BEAN LADIES MAINE HUNTING SHOES SZ 11 GREAT COND!!Ryka Fierce Women’s Black Purple Slip On Comfort Training Sneakers US 6.5 M B641NIKE Flex 2013 RN Women's 11 Blue Running Shoes Sneakers Trainers 580440-403 ,
"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."