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.Pre-Owned DANSKO Professional Clogs Black Leather Women's Size 36 (US 6)-NICE! , Born Crown Women's Ginni Ginger Leather 8.5MLucky Brand Emmie Women's Slip On Round Toe Ballet Flats ShoesClarks bendables 34963 Mule Heel Buckle Stitched Split Toe Slide Women's 7 M , Grasshoppers BLACK SHOES WOMENS SIZE 7 1/2 M , LONSOEN Women Moccasin Driving Shoes Casual Solid Leather Loafer Slip On Boat... , EUC *G.H.BASS & CO.* "WEEJUNS" "Bass Dee" Pink Leather,Slip On,Penny Loafer,7MKEEN Womens SIENNA Teal Blue Nubuck Leather Slip On Mary Janes Shoes Sz 10M NICEMerrell Encore Breeze Clogs - Women's Size 9.5, Dark EarthNWT Dillard's Dije Burgundy Faux Fur Suede Moccasins Size 7Women's NaturalSoul Naturalizer LEATHER Tan SANDALS SHOES 2" HEEL Size 8 M - EUCWomens Ecco Brown Leather Loafers Shoes Size 38 , Zaxy Pop Heart Flock Black Womens Ballerinas Flats ShoesDr Scholls Style Anna Taupe Canvas Womens Athletic Sneaker Size 11 , Pristine UNDER ARMOUR silver high tops soccer corpspeed shoes 11 or 10.5 M , FAUX SNAKESKIN SLIP-ON SNEAKER WOMEN LZZY-82-16 J’S AWAKE PEWTER , NIKE REVOLUTION TRAINING RUNNING SHOES - BLACK PURPLE WHITE ( SIZE 10 ) WOMEN`SNEW-REEBOK FURYLITE FG -BLUE W/Pink FLOWERS -WOMEN'S SNEAKERS SIZE 7.5 BD1097 , Brooks GTS 17 Gray Orange Powerstep Athletic Sneakers Women's 10 M / , Mojo Moxy Women's Maritime Fashion Sneaker, Flag, 7 M US , Women's CREEPER-113 Various Styles FlatsFila Men's Royalty 2 Running Shoe - Choose SZ/Color , Converse CT Tri Zip Hi.. White/ Blue/ Red.. Size 7.5.. Fast Shipping!! , Nike 807471 Womens Classic Cortez Leather Performance Running Shoes Sneakers , Italian Greyhound Dog Print Slip Ons For Women-Express Shipping , Womens Cole Haan Shoes Grand Crosscourt II Sneaker Black Suede White Size 8.5 BAsics Womens Size 11 IGS Gel Resolution Eclipse Tennis Shoes Running TrainingSAUCONY EXCURSION TR10 SNEAKERS WALKING RUNNING TRAIL WORK SHOES WOMENS SZ 7adidas Cloudfoam One Thong Women's Black/White/Grey B41746Gray Blue Skechers shoes Memory Foam Women sporty Comfort Casual Slip On 14140 ,
"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."