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.MIMOSAS Bonata Moccasins Slip On Flats All Leather Shoes 8M Brazil NEWRestricted Women's Black Perforated Ankle Strap Ballet Flats Sz / US 5.5Born Women Moc Toe SZ 8 Buckle Loafer Slip On Shoes Chestnut Brown Leather #C69HAFLINGER Germany Black Wool Slip On Mule Shoes, Size 42 , Drew Shoes Womens Size 5 Wide Black Mary Janes Heels 5W , BNWT ZARA STUDDED BLACK LEATHER LOAFERS SHOES SIZE US 8 , Cole Haan Woven Ballet Flats Air Bria - Comfort Slip On Leather Womens 8 B GoldCole Haan Women's Pink Zerogrand OS Wingtip Leather Oxford Shoes 5M , **Dr. Scholl's Glory Snake Embossed MicroSuede Flats, Women's Size 8.5M, BlackTahari Foley Loafer Ballet Flats, Slate , GEOX Respira Mocassins Cuir Beige T 39 TBEJane Shilton Ladies Tan Brown Leather 70s Retro Buckle Loafer ShoesLL Bean Womens 7.0 M TAN Suede Comfort Mocs Slip On Walking Hiking Trail Shoes , Sanuk Pair O Sail Boat Loafers Shoes White Waikiki Size 7 New , New Balance Women's 555 Shoes Black with Grey 11 BNike WMNS Free 5.0 TR Fit 5 Metallic V womens train training sneakers blackNew DC Shoes Girls Kids Court Graffik Sneaker Trainer Skate Casual White Sz 6Puma Eskiva Hi Deep Summer - Black - Womens , Nike Sweet Ace Womens Shoes 407992-050 Size 7.5 Black / Purple , Reebok Instapump Fury Jungle Book trainers shoe AQ9213 eu 37 us 6.5 NEW+BOX , Black Russian Terrier Print- (Black/White) Running Shoes For Women-Express Shipp , Women Vlado Footwear Shoes Siren Fashion Black Size 9 , Gola Women's Quota II Sneaker , EUC NIKE ROSHE RUN WOMEN'S ORANGE RUNNING SHOES US 8 51882-800 A2 , Nike Womens Gray Running Shoes Size 7.5 (24670)NIKE Air Force 1 Low Premium Red/White/Silver AF1 Shoes 350693-611 Women Sz 9.5Nike Women's INITIATOR Running Shoes White/Cherry-Metallic Silver 394053-101 c , NIKE ZOOM WOMEN'S LIGHTWEIGHT ATHLETIC SHOES~ SIZE 9M , Nike Air VP Running Shoes Orange Swoosh Sz 10 Woman's Cross TrainersSkechers Navy Coral Zen Bungee Slip on Walking Sneakers Shoe 10 W SALE
"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."