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.Clarks Artisan 66512 Kessa Agnes Mary Jane Loafers Women's Mismatch 9.5 & 9 MClarks Women's Leather Slip On Loafer Shoes Size 7 Various Styles , and ColorsNEW DISNEY PARKS Multicolor Suede Espadrilles Flat Shoes SZ 7 NEWsz 11 / 42 TS TAKING SHAPE Bronte Ballet Flats metallic finish comfy shoes NIB!CLASSIQUES PALLADIUM COULEUR SABLE T40 TBE COLLECTOR VINTAGE A ACH IMM FP REMaui Island Women's Shoes Beachcomber Tan Slip Sz 7.5Bamboo Womens Saili Metal Hardware T-strap Flat Sandal , Ecco Womens Slip On Oxfords Black US 9 - 9.5 Z522 , Minnetonka Womens twill junior trapper Closed Toe Charcoal Size 9.0 wKlQ , Crocs Freesail PlushLined Clog Female Ballerinas Clogs CrosLite Navy Blue , Tahari Womens Frankie Closed Toe Loafers Black Size 9.0 cIby , Easy Spirit Womens Devitt Leather Closed Toe Oxfords, White, Size 10.0 dRs5 , Donald J Pliner Blue Suede Moccasin Loafers 8 M Mosaic Silver Embroidered Top SW , Asics Women's Gel-Kanbarra 5 White/Lightning/Green Running Shoes 8MNEW Under Armour Speedfrom Womens Sneakers Size 7pastry black high top goth punk rock emo zipper chain buckle studded womens sz 7 , Skechers Womens Go Step Shoes Comfort Loafer 8 , Teva CHURN 4172 Women's 9 Bluejay Blue Gray Water Sport Shoes Sneakers EUC SZ 9Tommy Hilfiger Size 7.5M Gray Fabric Green Suede Active Sport Causal Tennis ShoeNike ACG Wildedge Womens Size 8 Waterproof Gore Tex , DR SCHOLLS Motion 8.5 AIR PILLO GEL SLIP ON Athletic Training Tennis ShoesPuma Morpheaus 341456 Purple Running Training Driving Sneakers Women's US 11Madden Girl Women's Airratic Fashion Sneaker, White Paris, 7.5 M US , K-Swiss Tubes Run 100 Women US Aqua Blue Black Cross Training Running 2644Allbirds Sz 7 Women's Wool Runners dark gray wool with white soles. GREAT shape! , ASICS GEL TORRANCE SMOKE BLUE BEGONIA WOMEN SHOES SIZE 6 , Merrell Moab Women's Dusty Olive Hiking Shoe 11MNew Balance Womens - Gray Running Shoes Size 6.5 (C,D,W) (421247)VANS Authentic SF (Joel Tudor) STV Navy Skate Shoes WOMEN'S 9 , Nike Air Force 1 Low Upstep Pinnacle Matte Grey 856477-001 WMNS New Size 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."