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.Brinley Co Womens Kinley Pointed Toe Loafers, Silver, Size 8.0 , womens rampage milian ankle strap flats shoes size 9 1/2 , NIB NINE WEST LADIES SIZE 6 PANDEY SLIP ON SNEAKER WHITE & STRIPES , Merrell "Spray Moss" Green Strappy Sport Water Slip-On Shoes, Size 9 , Clarks Blanche Fria Slip-On Shoes--Taupe Suede 6 wide store displayBorn Brown Leather Buckle Clog Mules Heels Size 10M 42 , New AK Anne Klein Sport Womens Autumn Fabric Ballet Flat sz 7.5M slip onMAM'ZELLE Mocassins P.37 (chausse grand = 38) daim noir , Bass Weejuns Catherine Penny Loafers Womens Size 11 M Brown Leather Slip-On Mocs , Ladies Equity Casual Shoes - Blossom , Ariat Yuma Size 7.5 B Boat Deck Shoes Brown Peach Womens Leather 10012908 Flats , ARIAT Mercer Brown Leather Women's size 7 B , CONVERSE ALL STAR DOUBLE TONGUE SEAFOAM & LIME GREEN LOW TOPS SIZE WOS 6Ladies Easyspirit Sport Shoe - Size 7.5Reef Pennington Flat White Women's Canvas Shoes Size US 8 /New , NEW Womens 361 Nocti-Lite Running Shoes Bright Rose / Pink - Choose Size , Converse All Star Tennis/basketball Shoes woman's Size 6.5 White/blue UsedMizuno Wave Evo Levitas 10 Womens Sneakers Shoes Purple Yellow AthleticMarc Fisher Chessi Fashion Sneakers 257, Bronze Multi, 6.5 US , Adidas Boost Continental Size 9 Blue Women’s , New Balance Womens 1980 Fresh Foam Blue Running Shoes 5.5 Medium (B,M) BHFO 9328 , NEW BALANCE Womens "Lacrosse" Field Cleats Black White Purple NIB SZ 6Brooks GTS 16 Running Shoe Women's Size 9 Blue Athletic Sneaker , Women's New Balance Wmns 792 Beautiful In Colour Athletic Shoes , Women's Bobs Women Size 8.5 New Varieties Are Introduced One After Another FlatsAdidas Originals Womens Superstar Coral Peach White Sneakers Shoes Size 8 NWT Q1Womens Nike Lunarconverge 852469-600 Lava Glow Brand New Size 9 , Converse All Star Big Eyelet Hi Women's Pure Platinum 560656C , New Balance WTE412S1 All Terrain Trail Running Shoes Sneakers Women's Sz 11Qupid Women's Picton-01 Fashion Sneaker - Choose SZ/Color ,
"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."