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.Sperry Top-Sider Bahama Greig Leopard Sequin Sneaker , Lauren Ralph Lauren CAROL Camel Brown Leather Slip On Flats Moccasins Sz.7,5B , 1.State Womens Skkylar Taupe Nubuck Ballet Flats Shoes 6 Medium (B,M) BHFO 0391SAS Free Time Brown Nubuck Leather Walking Comfort Oxfords Women's 5 M , Ballerine Souple Pliable Similicuir Style Ballib’s Semelle intérieur Cuir Cool ! , Clarks Shoes Women's Mules Clogs Brown Leather 2-1/4" Wedge Sz 9 M , Sperry Top-Sider for J. Crew Gold Leather Metallic Slip On Boat Shoes, Sz 8.5M , Cole Haan Country Women's Sz 8B Black Leather Career Lug Sole Loafers (box 37) , New Women Nature Breeze Luv-01 Metallic PU Espadrille Flatform Spectator Sneaker , COLE HAAN Womens Sz 5.5 Air Maggy Purple Suede Ballet Flats NEWClarks Neenah Garden Ballet Flats 168, Black, 7.5 US / 38 EU , Clarks Womens 6 M mules Clogs Slip on Casual loafers Shoes Brown Leather (18G)KENNETH COLE Alesy Blue Velvet Platform Slip On Floral Embroidered Sneakers 8 , MERRELL Primo Seam Petrol Blue Leather Women's Slide Mules Shoes Size 5.5Newton Women's Gravity - Orange/Lime (00210) Size 6 US 37 UK MESH RUBBERWomen’s bcbgmaxazria gold metallic pointy toe emlyn flats sz 9 buckle slip-on , "WORN ONCE" 37 6.5 6 BALLIN RED ITALIAN CROC SLIDE MULE SANDAL WOMENS SHOES , Vince Maxwell 2 Yellow Womens Shoes Size 8.5 M Flats MSRP $225 , Nike Womens Free 5.0 Run Running Shoes Raspberry Red Pink 580591-616 Size 11 , adidas Adilette CF Ultra Supercloud Plus Slides Blue White Mens Sandal AQ4936New Balance Women's WX88V1 Training Shoe-W, Blue/Red, 8 D US , NEW BALANCE Women Size 10 2E Gray WW847GY3 Motion Control Walking Shoes ZU-458 , Women's Nike ACG Outdoor Hiking Trail Boots Brown Leather 148057-221 Shoes sz 8New Saucony Womens Girlsexcursionshield-K Berry/Pink/Citron Fashion Shoes SizeWOMEN'S REEBOK WHITE LEATHER CROSS TRAINING SHOES SIZE 6 AIR CUSHIONING NWOTWomen's NEW VANS SK8-HI TOP SNEAKER Less Expensive Athletic Shoes , NEW Nike Air Max 1 Ultra Jcrd Jacquard 704999-500 Womens Shoes Trainers Sneakers , Hoka One One OdysseyWomen Running Shoes US Size 11 Black Gray Pink White F10015BNew Balance Women's 1165v1 Fresh Foam Walking Shoe Purple Size 5.0Brooks Womens Launch 5 Blue Running Shoes Size 11 (36988) ,
"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."