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 Shoes Chinese Flat Heel With Flower Embroidery Comfortable Canvas ShoesWomen’s Black Shoes Real Lather Modern Flats Size //USA 6Brown Leather Loafers Womens 9 Thom McAnEcco Monk Strap Walking Loafer Shoes Brown Leather Women's Size US 8-8.5 , Clarks Artisan Mary Jane Shoes Womens Size 7.5 M Black Leather Flats 26102762NEW Goby Cupcake Printed Flat, Women Size 6, $99Ballerines AEROSOLES Cuir Noir T 39.5 TTBESAM EDELMAN Women's Fashion Flats Shoe Size 9 , MINNETONKA Brown Suede 462 Moccasins (Size 7) , womens gold leather pointd toe maryjane dance shoes size 8 n , FitFlop 6M 37 Black White Leather Loafer Wedge Premium Slip On Casual Shoe Women , LPB ballerines femme AUSTINE jaune P38 neuves été 2016 , GENTLE SOULS by KENNETH COLE "Edge Slip"MUSHROOM BROWN Pull On Flat Size 6M ANBWomen's Shoes BC Burgundy Slip On Suede Patent Leather Studded Oxford Size 6.5 M , Vagabond Ayden Womens Bright Purple Suede Penny Loafer Style Moccasins New , Aldo New Bazovica Beige Womens Shoes Size 8 M Flats MSRP $70 , Steve Madden Gills-S Black and Gold US Size 8.5 M Sneakers NEWDOLCE by Mojo Moxy Womens Henna Pointed Toe Loafers, Black, Size 8.0New Balance W845NC Women US 11B Athletic Shoe White Blue 166-14Adidas Kanadia Road 2 Women's Running Athletic Shoes Size 11 MDirty Laundry Jump in Satin Sneaker - Women's size 6.5 - BlackSKECHERS Spot On Running Shoes, Women's Size 9.5, GreyLucky Brand Women's Jaleela Wedge Sandal Black Leather Heeled SandalsNike ROSHE ONE PREMIUM PLUS Women Running Training Shoes Green Purple 807614 453EUC Salomon SpeedCross 3 Pink Trail Running Shoes Sz 9.5Womens NEW BALANCE Running Shoe Sneaker Size 8 BNIB adidas ORIGINALS Tubular Defiant Women 6.5 WHITE nmd boost xr1 yeezy ultra , Nike Tanjun Racer Womens 921668-601 Tropical Pink Black Running Shoes Size 8.5 , Brooks GTS 18 Blue/Mint Running Shoes Women's US 10.5 (A4,20) , Dce Vita Tillie Knit Sneaker Sz 9 M Grey Mesh
"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."