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.NEW Gold slide slip on mules clogs FLAT loafers MOCCASIN women SHOES Size 5 , Jessica Simpson Womens Libra Taupe Ballet Flats Shoes 6 Medium (B,M) BHFO 9787Sesto Meucci Women's Black Leather Slip On Loafers Casual Size 7 B ShoesClarks Wave Walk 8 M Brown Leather Slip on Loafer 86564 ECDonald J Pliner Black Nylon Single Monk Oxford Flats Size 6.5MNEW Demonia Daisy Steampunk Brown Flats Shoes 8 Gears Clockwork Mary JanesNew Women's Sanuk Slip On, Size 6 , Cole Haan Air Womens 8B Flats Shoes Olive Green Gold Brown Suede Non-slip , Mix No 6 Vantage Women US 8 Black Flats Size 8Merrell Windsor Wine Expresso Hiking Casual Shoes Women's Size US 7/ , sandale compensées liege leopard ou creme semelle peau de peche 36 Au 41Cole Haan Womens 8 B M Air Tali Python Snake Ballet Flats Shoes Loafers Slip-On , Dansko Brown/Cordovan Leather Womens Mary Janes Shoes Portugal sz 38 US , SPERRY WOMENS CREST VIBE INDIGO STRIPE NAVY WHITE SIZE 9Naot Matai Leather & Brown/Bronze Suede Mary Jane Comfort Shoe SZ US 8-8.5ALLEN EDMONDS CHADWICK WOMENS SZ 10AA BROWN LEATHER KILTIE SLIP ON LOAFERS USA!Girls Women Smart Satin Pearls Loafers Sneakers Flat Heels Shoes Chic Trainers L , Puma Sneakers Blue White Women's Running Walking Shoes US Size 6 1/2 , Foamtreads Glendale Slippers - Men's Size 11.5, Black , Men's UNBRANDED brown w white faux fur Slip On Loafers Casual Slippers Shoes NEWHUSH PUPPIES Brown Leather Bedroom Slippers Slip On 12W , Skechers Go Run 600 Refine Running Women's Shoes Size , Vans Old Skool Dx Womens Gold Beige Textile TrainersWomen's Skechers GORUN FORZA Running Shoes 14SWOMEN'S/JUNIOR SHOES SNEAKERS LITE RACER [BC0073]adidas Women's Energy Cloud V Running Shoe, White/White/Crystal White S, 8 M USVans Chukka Moc DX (Suede) Atlantic Deep Women's Size 9.5Nike Lunarglide 8 Women's Running Shoes Size 6.5 - Women's 843726-502Womens ASICS GT-2000 3 T550N Running Training Athletic Shoes Gray Pink Size 6.5 , Womens Nike Lunareclipse + Shield Shoes Used Size 6.5 Trainers ,
"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."