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 Paso All Leather shoes, White , Minnetonka Backless Slipper Moccasins Black Suede Women’s Size 6 , Clarks Taupe Soft Cushion Mary Jane Flats Size 7.5W , 5/48 Saks Fifth Avenue Blue Snakeskin Casual Fashion Women Size 38 EUR/7.5 US , Enzo Angiolini Cranberry Bright Pink Slingback Leather Flats Shoes Womens 8N , Isaac Mizrahi Live! Menswear Suede Loafers with Bow 7 MEDIUM BORDEAUX NWDWOMENS LADIES FLAT TASSEL LOAFERS BROGUES SHOES TARTAN CHECK SCHOOL WORK SIZEFranco Sarto brown leather round toe buckle slip on loafer block heel 9WANTHROPOLOGIE All Black Alligator Snake Pointed Toe Flats Shoes Green Beige 7.5(417) Birkis Clogs Slip On Multi Color Flowers Shoe Women's Sz 7 , TORY BURCH REVA BLACK LEATHER BALLET FLATS~7Klogs Trixie Women's Leather Clogs Display Model Shoes Black Tintoretto 9 W , Botkier Maxine Peep Toe Clay Suede Slip-On Shoe Flats Size 8.5 New! $89Pewter Satin Stylish Tennies "Jena" by Mossimo Supply Co 11M NEW , New Balance 770 Women's Sneakers Size 9 BSIZE 9 Women's Black & Floral Athletic Sneakers Comfortable High Heel Shoes , Nike Woman's Dunk High Skibny shoes size 6 , LADIES WOMENS GIRLS CANVAS PLIMSOLES PLIMSOLLS TRAINERS PUMPS , Womens Flats Pumps Loafers Round Toe Shoes Casual Driving Slip on Suede BrownADIDAS THRASHER WOMEN'S RUNNING SHOE BLACK/PURPLE/GREY SIZE US 8 S2242017 New Brieten Women's Olive Green Round Toe Pom Pom Flat Shoes , Converse womans red white striped green christmas womans size 6 mens 4 sneakers , Ladies womens hidden heels wedge trainers zip Fur Lined boots shoes Sneakers newPropet Stability Walker - Womens W2034 White Size 5.5 2E (x)Women's Women's Skechers GoWalk Joy Shoe Big Clearance Sale Athletic Shoes , Puma Basket Platform Pineapple Gold White Trainer Girls Sz 7C US , Women's Salomon XA 3D Ultra 2 Hiking Trail Running Shoes (Sz:8)VANS SK8 Hi Slim Zip (Iridescent Eyelets) Black Skate Shoes Women's 6SKECHERS TWO pairs Womens tone up sandals size US 10, 27cm. , Corkys Footwear Women's Joann Elastic Athletic 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."