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.RANGONI Women Ballet Flats Size 9B Black Formal Slip On Leather , Hush Puppies Women's Suede Boat Shoes Size 7 Slip On Tan , Ballerines ROXY Velours Noir Confortables T 38 TTBE , Bamboo- Lasercut flower dust pink/ nude, brown summer women flat shoes size US6 , NORTHSIDE T 312304W WOMENS NEW VERGLAS BALLET SLIP ON SHOES US 7 , LADIES SPOT ON LIGHT PURPLE FLAT SHOE WITH BOW "F8670" , vintage tan olive Embellished tooled leather MARY JANE flats sandal shoes 7 NICECute Animal Hamster Women's 3D Print Casual Loafers Flats Breathable Fisherman , Vintage Turkish Handmade Leather Soles Ethnic Point Toe Shoes Womens sz 5Ryka LIBERTY 591421 Womens 7.5 White Leather Mesh ORTHOLITE Athletic Shoes NEW , Aerosoles Womens Traveler Flat- Pick SZ/Color. , Merrell Forecast Moc Women's Black Leather Waterproof Insulated Shoes - US 10 , Twisted X Women's Blue Canvas Striped Driving Mocs WDM0048 Super Comfy - SALE!!! , Skechers Women's Side Street-Core-Set Sneaker, Light Pink, Size 8.0 MTGiASICS Womens Gel-Venture5-W Blue Running Shoes Size 9.5 (333837)Tommy Hilfiger*Women’s 9.5 M*Back-Strap*Blue/Red Plaid*Slip-On Platform W31104Chuck Taylor All Star Hi Turbo Green Sneaker big kid 5 fits woman 6 1/2New Women's Skechers Empire Inside Look Slip On Casual Shoes 12419 Gry/Wht dc 0RThe North Face Litewave Explore Trail Running Sneaker Womans Sz 6.5 Pink & Blue , NEW SPERRY $75 Rave Verge High-Top Casual Sneakers Shoes Women's Black US 7.5Nike 394656-041 Air Prestige III 3 Athletic Gray Fashion Sneakers Women's US 9Steve Madden Gracy Sneaker - Women's Size 8, TanFashion women Shoes Muffin Flat Casual British Wind Fashion Breathable Shoes , Asics Gel Quickwalk 2 Sneaker - Women's Size 9.5, Purple/Pink (DAMAGED) , Vasque Constant Velocity Women's Rabbit/Poppy Red 6.5MNew New Balance Womens Wt910gx2 Grey/Pink Cross Training Shoes Size 5 (C,D,W) , Skechers Women's Go Walk Lite-15395 Ballet Flat - Choose SZ/ColorNike Vandal Low Red White Blue Sneakers Womens Sz 7.5 Hard Rare Color , New NIKE 749180-003 Women Core Motion TR 2 Mesh Training Lightweight Shoe sz 7MMerrell Castle/Rock Periwinkle Performance Footwear Shoes, Women’s Size 8 ,
"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."