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.NICOLE Leather Suede Flat Oxford Mule Sandal WOMENS Shoe Size 6.5Madden Girl by Steve Madden Womens Grace Black Casual Shoes 7 Medium (B,M) 2125SAS Roamer Mary Jane Shoes ~ Women's US Sz 8.5 N ~ Black ~ MSRP $167 , Ladies Black / Gold Spot On Dolly Shoes UK Sizes 3 - 8 F8863Decree Women's Shoes Size Us 8M/Eur 39 Brown Suede Leather Moc Toe Loafers Flat , TALBOTS Women US 7M Black Patent Leather Raised Loafer Career Dress Made Italywomens anne klein talin multi colored skin print loafers shoes size 7 1/2New women's shoes bow ballerina ballet flats wedding casual BurgundySalvatore Ferragamo loafer Gold logo buckle black Womens 7.5 AAAA narrow , Mix No 6 Womens Sarlinas Almond Toe Loafers, Black, Size 7.0 j0ujCORSO COMO WOMEN'S PYTHON S18890 BALLET FLAT NUDE DULL SNAKE LEATHER SIZE 6 MED , DANSKO Womens shoes (7.5/US 38/EU) NEW , Keds 6.5 M WH14169WH6CH17 Leather Sneaker, Beige Leather , MARC JACOBS BORDEUX LEATHER POINTED TOE PERFORATED FLATS 39 9[SEED HERITAGE] NEW ‘Monica T-Bar’ Sandals - White - Sizes 38, 39, 40, 41 , Land’s End Vented Water Shoes Womens Sz 6 D White Blue LeatherSkechers Womens - White Walking Shoes Size 10.5 (366401) , Asics GEL-Cumulus 17 Women's Aqua Mint/Yellow/Navy Running Shoe 7.5MSPERRY TOP-SIDER "BLUEFISH" LEATHER SHOES LADIES US 7 MED EURO 37.5 NEW , Sketchers Women's Shape-Ups Fitness Walking Shoes 11814 Sz 8.5 No Insoles , NIKE REAX RUNNING SHOES BLUE BLACK 454175-004 Womens Size 11Skechers Performance Women's Go Run 600 RefineBlack/White8.5 M US , BOBS from Skechers 34166 Womens Sunset Fashion Sneaker- Choose SZ/Color. , New Nike Womens Air Force 1 HI SE Athletic Shoes Sneakers 860544-001 Sz 7.5 , Nike Women's Free TR Fit 5 Training Shoes NEW White/Red MSRP $100Women's Converse Chuck Taylor All Star CTAS Shoreline Slip Navy 537080F NWOBNike Women's Running Shoe Core Motion TR 2 Mesh 749180-011 Women Sz. 5.5~8 , Asics Gel Evolution 6 Gray Running Training Shoes Women's Size 8Nike Air Max Thea Gym Red Womens Size 10 599409-606 j1 , MBT Sport 02 White Leather Athletic Rocker Walking Shoe Size Womens 7 ,
"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."