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.Crocs Women Purple Brown Flat Ballets Purple Bow Slip Ons Size US 10 Excellent , Clarks ARTISAN UNSTRUCTURED BLACK SHOES WOMENS SIZE 8 1/2 MCROCS WIONA Antique Flat Shoes~Brown Espresso~Womens Size 4NEW VANELI $110 8 narrow Leather brown sft grain shoes mocassin oxfords low heel , G. H. Bass Women's Leather Boat Shoes Size 7 1/2 M , Mojari Indian Handmade Women Shoes Leather Sandals Loafers Slippers Flat US 6-9 , WOMENS NAOT MARY JANE 39 8.5-9 BLACK LEATHER SHOES TOP STRAP ~ NICE WOMENS , Women's J Crew Sz 6 Oxfords Shoes Saddlebrook Brown Black Leather Made Italy N2Jessica Simpson Women's Mandayss Ballet Flat,Black,8 M USCrocs Tembo Polartec BN with Tags , Trotters Womens Francie Closed Toe Loafers Brown Size 11.0Marc by Marc Jacobs round toe duck boots water proof gray and red size 38 , COS Nude Pink 100% leather Slip On Sneakers 6/6.5 36 37 , ☼ELEN☼ Ballerines SUREDELLE - Ref:GE23 BRONZE , Salvatore Ferragamo Women's Brown Leather Brogues in Size 8 , ED Ellen DeGeneres Womens Wallita Rain Bootie, MultiColor, Size 8.0 sNLQWomen's size 10 Brooks Ghost shoes in grey and turqoise. , Keen purple yellow breathable cross training hiking athletic shoes ladies 7.5 , Pastry Women's Size 7.5 Gray Patent Hi Top Dance Cheer Sneakers Athletic ShoesWOMEN'S ASICS - GEL-QUANTUM 180 (T5J7N-4235) - SIZE 11 - 50% OFF CLEARANCENew 6605 Athletic Orthotic, Diabetic Shoes by PG Lite women's size 10B , NEW J SLIDES SZ 9 PAGE PEWTER LEATHER SLIP ON LOAFERS SNEAKERS , Scarpa Hiking Shoes 32043-352 TRV Trail Running Shoes Gray/Pink 2U15 Women's 7.5 , PUMA FIRST ROUND L WHITE BRIGHT GREEN YELLOW WOMENS WMNS SZ 8.5-12 347073-07Converse Women's All Star Madison OX Black/White/Purple Sneakers - Size 6.5 NWB , Sketchers Los Angeles Womens Sz 9 Leather Sneaker Black Gold Memory Foam Hi LiteVANS Chima Ferguson Pro (Aloha) Light Grey UltraCush MEN'S 7 WOMEN'S 8.5NIKE WOMEN'S TENNIS CLASSIC SHOES SIZE 11 white black 312498 130Baskets Femme samples shoes ETNIES VOLT WHITE GREY BLUE WOMENRyka Womens Leisure, Bougainvillea/Robin, Size 7.5 AkVm ,
"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."