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.Easy Spirit Espadrilles Shoes 5 Two Pair Blue Beige Women's 5 MSkull Slip On Boat Shoes Women Canvas Loafers Comfy Flat Slacker Shoe Girls , Clarks slip on shoes Green Leather mules sz 9M clog comfort Stitched , Clarks Bendables Patent Croc Print Moc Loafers Slip On Black 26064894 Womens 6W , Women's Rockport SV75727 Oxfords Shoes Size 7M Brown Leather Wingtip Brogue G9 , basic editions comfort work shoes size 8 wide. Navy , SANUK MIKA MULTI NORDIC SIDEWALK SURFER SHOES, SIZE US 6/ ~NWT , Keen Womens sandals waterproof size 10 , Aldo Phinney Oxford Loafer Woman US8 EUR39 (Brand New with a Box) , Cole Haan Silver Leather Cap Toe Bow Ballet Flats Womens 7.5 B Pre OwnedTrotters Americana Slip On Shoe - Women's Size 7W, Natural Canvas , Womens Sneakers Flats Athletic Breathable Sport Summer causal Mesh Shoes yooocar , Womens Round Toe Flat heel Caual Athletic Fashion Sneakers Slip On Shoes Loafers , Clarks Women's Sillian Free Clog , NEW Disney Store Minnie Mouse Mary Jane Costume Shoes Girls Size 13-1 MickeyNWT Tom's Women's Glitters Classic Slip-On 100% AuthenticDansko Professionals Summer Clogs Black Leather US 10 10.5 , Crocs Womens Swiftwater Cross-Strap Black/White Fashion Sneaker Size 9 (18687) , **Dr. Scholl's Atlas Knit Shoe - Women's Size 8.5 M, Grey DISPLAY , New Balance Women Size 7.5 Silver Green 590 V5 Speed Ride Running ShoePUMA PC WEDGE SPORT 357287 40 Dubarry Black Active Life Style WOMEN SIZE 7 , MERRELL VIBRAM RUNNING SHOES - GREY PARADISE PINK ( SIZE 6 ) WOMEN`S , Women's VivoBarefoot Women's Athletic Shoes Beautiful Design Athletic Shoes , Adidas Originals Sneakers Shoes SZ 7.5 /Women's Puma Trace Platform Sneakers Shimmer blue Pink Size 7British Shorthair Cat Christmas Print Running Shoes For Women-Free Shipping , Havana Last Jeffrey Campbell Navy Blue 10k Run Mesh Leather Sneaker Shoe 7.5M 38 , NEW Nike Women’s Air Max Kantara Lagoon Blue 908992-400 Sz 6 NEWClarks 26120279: Women's Gold/Metallic Keesha Rosa Dress Pump , New Balance Women's W790 Ankle-High Running Shoe ,
"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."