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.Handmade Women's Traditional Velvet Flat Shoes Casual Ethnic US 4 5 6 7 8 9 Size , Women's Sperry Top-Sider 9776774 Sz 10M Yellow Cream Casual Boat Shoes Floral M7Women Men Fashion stylish Casual Health Canvas Flat Shoes - Mint size 36Coeo+Sam Dusty Orthotic Friendly Summer Shoes , NWOB MINNETONKA BROWN LEATHER SUEDE UPPERS Size 9 MOCCASIN SHOESKelly & Katie Womens lovelian Closed Toe Loafers Navy Size 7.0 u6Rq$140 MISS SIXTY MARLENE Oasis Beige Suede Designer Slip On Loafers 6.5 , Alice Olivia Piper Black / White Women's Fashion Slip On Flat Loafer 40 / 10 M , Kenneth Cole New York Womens Wilhelmina Pointed Toe Ankle Strap, Rose, Size 8.5French Connection Women USA 8 Oxford Shoes Metal Tipped Brown Leather -S1220 ECCO Soft 7 Gray Nubuck Leather Front Zip Fashion Sneaker Women Size 37 M , Cole Haan Womens Red Patent Leather Penny Loafers Slip On Shoes Size 6.5 BSkechers Sport Women's Women's Microburst Darling Dash Sneaker , Womens Easy Street 40-3240 Blue Flats 7.5 M , W52006 Women's BORN CHIANTI Susy Burgundy Suede 7.5W , New Reebok Womens Print Run 2.0 Black Running Shoes Size 8.5 , womens 8.5 classic Vans shoes sneakers blue Hello Kitty SO CUTE! , Reebok Ziglite Women's Running Athletic Shoes Size 9 MVibram Fivefingers KSO Blk/Blk Ladies 36 , Women's Ladies Suave Casual Shoes Lucy Clearance Price FlatsNIB - UNDER ARMOUR RUN FIT LO 1297606 769 White RUNNING SHOES - 6.5 / 37.5Under Armour Women's Micro G Press , Vintage Fila Shoes Black White Feb 96 Old Skool Original Youth Size 5 , NIKE FREE RN MOTION FLYKNIT WOMEN`S SHOES TRAINING RUNNING SNEAKERS NEW SZ 12 , Brooks Glycerin 12 Women's SIZE 11N Running Shoes Blue Aqua TrailASICS Womens C700y.9601 GlacierGrey/White/RougeRed Running Shoes Size 6 (424364) , Skechers Womens Easy Going Repute Mule- Select SZ/Color.Nike Wmns Benassi Duo Ultra Slide White/Metallic Silver 2017 Sandals 819717-100Vans SK8 Hi Moc Tortoise Black Blanc de Blanc Women's Size: 5.5AVIA MOTION SHAPE-UPS BLACK WHITE RUNNING TRAINING TONING WOMENS SIZE 7.5M ,
"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."