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.ROS HOMMERSON Womens CADY Black Nappa Skimmers Size 6.5SS (74007-12)Waldlaufer "Hazel" Black Leather Loafers Shoes US 7 Near Mint $145Spot On Ladies Flat Black Patent Tassle Shoe F8712 UK Sizes 3 X 8 (R2A) , Sesto Meucci Alcyon Cognac Print Amy 6405 Size 7M Suede Slip On Loafer Flat**Crocs Carlie Graphic Cutout Clog - Women's Size 8, Vibrant Violet , NOS NEW VTG Minnetonka Moccasins Shoes Womens 8 Brown Leather Suede USA , Dolce Vita Women's Cooper Oxford, Charcoal Velvet, Size 6.0Klogs Isabella Women's Leather Clogs Display Shoes Model Black 9.5 MCOLEHAAN LADIES SHOES new never worn in original box size 7.5 B Grant Blaze , SKECHERS GORUN 400 SOLE White Size 11 Sneaker ShoesKeds Kickstart Sneaker- Women's Size 5.5, White , MERRELL women's Jungle Moc Gunsmoke shoes size 7.5 J60788ASICS Women's GEL-Survey 2 T453N 4001 TURQUOISE/WHITE/LIGHT Size 6.5 (US)Women's Asics GT 2000 V 4 Running Shoes 7 Black Turquoise Yellow T656N , MERRELL Womens 7.5 Siren Ventilator Trail Hiking Shoe Low Top Brown Desert SageIsola Hailey Womens Shoes Pumps 9.5 Brown Leather Tassel Block Heel CareerLadies ADDIDAS RUNNING SNEAKER SIze 9.5ECCO powered By Receptor Technology Woman Size L US Sz 7/7.5 style 381460 , **Asics FuzeX Rush Athletic Shoes - Women's Size 9.5, Pink/Black , New Nike Womens Free TR Flyknit 2 Running Shoes 904658-006 sz 7.5 Multi-color , Nike Air Force 1 '07 Seasonal Women's Shoes Black/Anthra/Sail 11.5 818594-003Women's Nike Free TR 6 Training & Running Shoe 833413 001 Size 5 Black/WhiteChow Chow Print Sneakers For Women- Free ShippingReebok BD5758 Womens Club c 85 Syn Fashion Sneaker- Choose SZ/Color. , Wmns Nike Lunarstelos Blue Black Women Running Shoes Sneakers Trainer 844736-402adidas GAZELLE - White - Womens , New Balance Silent Hunter Racing women track spike WMD500O4 Orange Navy PinkSaucony Originals Women's Jazz Original Sneaker, Coral Cream, 7.5 M USSam Edelman Platform Sneakers Size 9 Womens Pink Rose Satin Slip On Frayed Trim , Northside Women's Apex Lite Waterproof Hiking Boot, Medium Brown/Teal, Size 6.5 ,
"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."