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.Fossil Sassy Charm Flat Ballet Flats Shoes Brick Red Leather Size 7 New! NIB , Womens Sperry Top Sider Shoes Size 8.5 , NEW Womens Tennis Shoes Size 9 Black Mary Janes Flats Canvas Casual Sneakers , Skechers Cali 36674 Women's Pink & Brown Canvas Slip On Sneaker Shoe 8.5 M , NWOB - ROCKPORT Black Mary Janes Shoes - Size 6M Buckle close , Born Women's Brown Leather Mary Jane Size 8 M US Eur 39 Style W61794Women's Clarks Wave Crest Loafers Shoes Size 6M Waterproof Gray Suede Outdoor R8 , Sofft Euro Soft Women's Dk Brown Wedge Slip Ons 8.5M Loafers Stretch Casual , CLARKS BENDABLES 38629 Wo's 7M Black Leather Wedge Loafer Slip OnCLINIC Woman's BLACK Leather Loafers Moccasin Slip On Comfortable Shoes 11N USKlogs Shelby Womens Clogs Shoes Display Model Leather Driftwood 9 W , Birkenstock Clog Slide Shoes Women's Sz 5m Blush Color Leather (tu34)T.U.K. Metallic Loafer Slip On Creeper . Womens Slip-On- Choose SZ/Color. , Vince Camuto Women's Dayna BITTERSWEET GRAPEFRUIT Size 7.0**NEW** Unstitched Gusto Espadrill shoes Women`s Size 9 U.S.Color. Hot Pink. , Womens Rivets Moccasin Slip On Flat Loafers Ladies Casual Ballerina Ballet ShoesBass Ursula Strappy Slide Sandal 9 M Black New with Box , Nike Air Force 1 Women Size Us 6 , Skecher Sport Energy Optimum Casual, White, Leather,Women's US 7.5Converse All Star Men Size 11 Women 13 Black Canvas Shoe Sneakers Excellent -A1 , 5.10 FIVE TEN INSIGHT HIKING WOMENS Walking SHOES SIZE 7Skechers Women's You Define Sneaker Navy/Blue Size 13.0Skechers Shape-Ups Jump Start Fitness Walking Shoes Womens Sz 9 White Blue 11803 , BZ521 2 STAR shoes white leather glitter women sneakersNike Air Max 1 Ultra Moire Women’s Running Shoe Black White 704995-001 , Nike Air Zoom Structure 19 Flash Women's Shoes 806579-001 aWomens Nike LUNAR BALLISTEG Shoes White SIZE 37, 5!!! DB , New Balance WF616 Fitness Shoe-W Womens Shoe- Choose SZ/Color.A65 Nike Women's Air Max Thea Sneakers 819639-100 Size 11 New Retail $100New Womens Mesh Slip On Loafers Wedge Heel Casual Athletic Shoes Sneakers Y1026
"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."