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.ZUMFOOT Women's Size 37 (6.5-7 US) Brown Leather/Suede Mary Jane Casual ShoesNew Women Breckelles Talia-53W Glitter Shimmer Pointy Toe Studded Ballet Flat Sz , Mint & Rose Portofino Khaki Salmon Leather SlipOn Espadrille Flat 8M 39 $160Mules Pocket P.36/37 (T.2) Vintage Fleuries , DANSKOS CAROL LOAFER FLAT BLK SUEDE LEATHER SIZE 9, 9.5 / 40 MEDIUM PRE-OWN , Anne Klein Zasa White Womens Shoes Size 6 M Flats MSRP $75 , Miu Miu Brown Leather Moccasin Ballet Flat Shoe Size 39 9 , AEROSOLES 8W Tan Natural Laser Cut Leather StitchNTum BOI OH BOI Dress FlatsNWT CROCS DASHER LINED CLOGS ESPRESSO BROWN BLACK REALTREE CAMO 4 6 8 9 10 11 12 , Clarks Kessa Betty Leather Artisan Hook Loafers Tan Shoes Women's 6 M , CLARKS Women's Rosilla Hollis Black Snake Leather 6.5 B USNew Women's Skechers Bobs Slip-on Casual Flats (39571) (J28) Size 7 , New Balance 758 TS2 Breathable Athletic Running Walking Shoes Women's Size 10.5DR COMFORT Collette Women's White Leather Casual Comfort Shoes 9W DiabeticNIKE Pegasus 30 Women’s Pink Black Running Shoe H2O Repel Sz 10 Sneaker , Brooks Women's Addiction Walker Leather Walking Shoes Sz 7.5 BAdidas NEO Renewal Leather Trainers White/Black G52947 Women Shoes Size 8 , Nike Reflective Purple Blazer 317808-501 Women's Size 9.5 Hi tops sneakers shoes , New! Saucony Women's PowerGrid Triumph 10 in Blue Size: 5.5 in box , CY7 WOMEN'S SHOES 37 HIGH SNEAKERS CYCLE LEATHER GREEN LIST PRICEMerrell Moab Womens Sz 6 Hiking Trail Athletic Shoes , Nike Roshe Two 2 Flyknit Womens 7.5 College Navy/Binary Blue/Vapor Green/White , Women Reebok BD4897 Skyscape Run Around Casual shoes black white sneakers , NIKE WOMENS FLEX SUPREME TR 5 TRAINING SHOES , Pearl Izumi Streak Running Shoes Women Size UEC 40 US 9.5 , New Balance WL574HRG Grey Black Pink Green Women Sneakers Casual SZ 5 , Woman Reef Fanning Sandal Flip Flop RF1626 Black / Grey 100% Original Brand New , Nike Darwin Bright Mango/Bright Mango-Bright Crimson (WS) (819959 881)Adidas Originals White Mountaineering Energy Boost Uni Classic Trainers Ltd Edit , AVIA WOMENS ATHLETIC SHOES SIZE 9.5 MEMORY FOAM WHITE PINK LADIES CASUAL STYLISH
"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."