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.I35 Caleyy7 Espadrilles 173, Silver, 8.5 US , Lauren Ralph Lauren womens cortney espadrille shoes sandals wedges 9.5 tan , NAOT Navy Blue Leather Wedge Mary Janes Straps Shoes Women's 37 US Size 6MKlogs Fisher Clogs Leather Display Model Shoes Tex Mex 6 MKLOGS CLOGS BRISBY WOMEN'S DISPLAY MODEL SHOES BLACK SMOOTH 9 MDansko Vegan Blue Denim Embroidered Slip On Clog Sandals Womens Sz US 8.5-9 EU39 , Clarks Muckers Womens Shoe Size 6 Brown Suede Leather Waterproof Moccasins , NIKE ZOOM TRAINER Black White Running Shoes 324514-011 Womens SIZE 9.5 , Reebok Sublite Women's Grey/Aqua Athletic Running Shoes Size 9 , Womens Woven Shoes Slip On Elastic Flat Shoes Breathable Casual Sandals Fashion , Ballerines MODA VIRUS Cuir Marron Fauve T 36 TTBENIB Softwalk Soft Walk TAYLOR Brown Mary Janes Comfort 8.5 8 1/2 MEDIUM , DR. SCHOLLS Womens 7.5 W Wide Walking Shoe Slip On Beige Tan Leather Ballet Flat , Womens Asics Gel GT 2000 Running Training shoes size 6.5 T2K7N , Teva Refugio Hiking Shoes Blue/Teal Women's US Size 7 (K2,17)CROCS BAYA FLIP 44-48 NEW Thongs slides Bathing-shoes sandals slippers shoesMen's breathable Baotou soft leather flat-bottomed slippers , Sanita Water O2 Shoes Blue/Purple Mary Jane Knitted Slip Resistant , Rocket Dog Women's Canyon Slip-On Sneaker , Saucony Power Grid Xodus Trail Training Running Womens 9 US Shoes Purple/Orange , Women's NATURALIZER PATENT LEATHER CROCODILE 6.5W Reliable Quality FlatsNEW in BOX PUMA Cell Tolero White w/ Pink Satin & Silver Running Shoe Sneaker 12VANS Sk8 Hi Slim (Vintage Suede) Amber Gold Skate Shoes MEN'S 3.5 WOMEN'S 5ECCO Womens size 5 - 5.5 Receptor Summer Trail Hiking Walking Shoes BxCOnitsuka Tiger by Asics Womens Mexico 66 Slip-On- Select SZ/Color. , Merrell Jungle Moc Gunsmoke Walking Hiking Outdoor Shoes Suede Womens Sz 8?Merrell Moab Women's Dusty Olive Hiking Shoe 6.5M , DR. COMFORT BEIGE LEATHER SNEAKERS DIABETES WALKING SHOES US WOMENS SZ 4.5 XW , Women's NWOB SKECHERS GOwalk 3 INSIGHT 13983/HPK Size us 9.5-BALTRA OLYMPUS ANTI GRAVITY TRAIL RUNNING X COUNTRY SHOES US W'S SZ 8 ,
"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."