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.New 6 1/2 AMANDA FLATS LILAC Croc LIZARD Womens Sz 6.5M LT ROSE Loafers shoes , Dimmi Footwear Adventure Women's Shoes Sz 6 1/2 6.5 Color Red Charcoal CinnamonV1 AGL Attilio Giusti Leombruni Pink Suede Ballet Flats Women's Size 36 M , Cobb Hill By New Balance Womens Flats Shoes Brown Leather Size 8Wide Walking , LADIES DOWN TO EARTH RED COATED LEATHER RIPTAPE STRAP FLAT SHOE STYLE - F80066 , Womens Grasshopper Black Wedge Casual Shoes Size 7.5M (S270)Eeko Womens Black Slip Ons Size 7 MCole Haan Women's Brown Loafers With Silver Chain Link Buckle Size 7 AA D20972 , Bass Womens Grayson-1 Leather Oxford Casual Ballet Flats Wht/Blk Houndstth 6 9 MEtienne Aigner Women's Leather Brown Shoe Loafers Logo Tassels 8.5 M Slip On EUC , Sperry Top-Sider x Jaws Movie Seacoast Red Casual Canvas Shoes Sz 9 NEW STS97115ALLEN EDMONDS CHADWICK WOMENS SZ 10AA BROWN LEATHER KILTIE SLIP ON LOAFERS USA!Dr. Scholl's Ashah Pointed Toe Flat- SIZE 8- BLACK- $99 , Spot On Ladies Hi-Top Canvas Pumps. X0002 Burgundy Sizes 3 x 6 (R6B) , Mary Janes Womens Girls Pointy Toes Zipper Flat Heels Dress Ballet Shoes Casual , Naturalizer Womens Saban Leather Closed Toe Loafers Black Size 7.0 kPOq , Sperry Top Sider Audrey Women 6.5 M Pink Moc Toe Boat Shoe Comfort Flats LeatherElaine Turner Women's Blake Black Sequin Ballerina Loafer Flat , Columbia Women's Switchback 2 Low Trail Running Shoes Size 8 Grey Purple BL3674INSOLES! NIKKEN CARDIOSTRIDES STYLE F SIZE 10 INCLUDING MAGNETIC INSOLES VGUCWomen's Sneakers Rose Us Polo Ronalda Promotions Athletic ShoesWomen's Authentic Prada Women’s Black Loafers Numerous In Variety FlatsVans Disney Pixar Toy Story Bo Peep Sneakers Shoes Sz 10 High Tops Off The WallNike SB Zoom Canvas Stefan Janoski Sky/Gold/Vivid Sky Sz 5.5 855628-447 , Mizuno Mizuno Synchro SL W Purple White Women Running Shoes Sneakers J1GF16-2866Skechers Performance Women's Go Step Lite-Endure Walking ShoeBlack8.5 M US , NEW IN BOX WOMEN'S 5 SUPRA SKYTOP ROSE GOLD METALIC WHITE HI TOP SKATE SHOES , ASICS GEL XALION 2 C439N-2093 RASPBERRY WOMEN'S RUNNING JOGGING OUTDOOR TRAINERSNike Prime Hype DF 2016 Black White Basketball Shoes 844792-001 Womens Size 8 , Adidas Womens Rockadia Trail Black/White/EasyOrange Trail / Hiking Shoes Size 10 ,
"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."