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.Sofft Black Leather Flats BOTIJA Style Sz.7nN.Y.L.A SCOTTY FLAT WOMEN'S BLACK US SIZE 6M NEW/ DISPLAYNWOT WOMENS ANNE KLEIN FLATS SIZE 8 RETAIL $100Rajasthani Women Black wedge Sandals Ethnic Flip Flops Casual Shoe Flat SleeperWomen's Kustom San Juan Fiesta Sandals / Shoes, Size 7-8. NIB, RRP $49.99.J. Crew Zoe Sz 6M D'Orsay Pointed Toe Flats Blue Suede Women's Shoes Royal BlueKendall + Kylie Womens Jules 3 Black Espadrilles 9.5 Medium (B,M) BHFO 8293 , Merrell Orbit Women's Moccasins Classic Taupe Suede Size 7.5(US)Chinese Laundry Endless Slip On - Women's Size 7 Snakeskin , Women Casual Fashion Thick Soled ShoesLUCKY BRAND Crochet Slip on Flats White Women's Sz 10M , CLARKS CADDELL DENALI Women Loafers (8.5 N, BURGUNDY) , Women Flamingo Canvas Shoes Causal Shoes Comfortable Moccasin Zapatos HombreVans Aqua Teal Blue Canvas Sneakers 6.5 , NUC WOMEN'S 7.5M GOLD GLITTER SPERRY TOP SIDER BOAT SHOE SNEAKERS NICEJessica Simpson Women's Mackson Ballet Flat , Nine West Women's Shutout Fabric Loafer Flat Black/Black Size 11.0 oqJLIrregular Choice Star Wars C3PO Shoes Size 9 Princess Leia Luke Sky Walker NIBCircus by Sam Edelman Women's Carmela Sneaker, Pearl Pink, Size 8.0Women's Shoes; Via Spiga; Size 8 1/2; BlackASH ITALIA Women's Spirit Sneaker - Starlight/Black - Multi SZ NIB - MSRP $195 , vintage LE COQ SPORTIF Wendon Nylon red 50562 taille 37 us 5 SIZE JP 23 , WMNS NIKE FREE TR 7 WHITE ROSE VOLT TRAINING RUNNING SHOES 904651 102 US 8.5 NEWConverse CTAS Leather + Faux Fur Chelsea Boot Black Gold 553392C Women’s Sz 9Nike Women's FREE 5.0 TR FIT 5 PRINT Shoes Black/Pink 704695-011 a1ASICS Womens - Blue Running Shoes Size 9 (326535) , New Nike Womens Lunartempo 2 Running Shoes 818098-408 Sz 9Nike Duel Racer Women's 927243 004 Athletic Snickers Training Shoes Gray Black , Skechers Women's YOU Zen Slip-On Sneaker , Vans AUTHENTIC Mono Surplus Microchip Women's Shoes 9 - Men 7.5 ,
"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."