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.BOISSY Toile Velcro JE 678A6 BleuEUC Women's 8.5 GH BASS Andover Earth Blue Leather Comfort Tassle Loafers ShoesCHRISTIAN Dior ballet flats size 38 cracked metallic gold black uniqueWOMEN'S GRAY LEVI'S TENNIS SHOE SIZE 8.5HPLA Womens Shoes Sz 6.5 M US Red Slipons Casual Dress Flats Loafers LaraWomens Size 40/9 Helle Comfort by Romu's Brown Patent Croc Print LoafersEcco Womens Black Leather Mary Jane Flats Size 41 US 10 , Merrell Primo Seam Moc 8 Shoes Dark Taupe Women's Brown Slip On ComfortVia Spiga Snakeprint Leather Oren Buckle Flats Beige Black Gold Size 8.5M , Clarks Artisan Collection Woven Brown Leather mule. Size 6M , Mens Clarks Artisan Size 8 Leather Slip On Dress Shoes Red Black EUC , Banana Republic Sz. 7 Donni Navy Haircalf SlingbackNine West Womens marie Leather Closed Toe Ballet Flats2018 Bling Womens Casual Shoes Spring Autumn Breathable women Shoes WedgesSteve Madden Womens Leather Zebra Stripe Ballet Flats with Cap Toe - Shoe 6.5MEscarpins Ballerines ALIMA Toile et Cuir T 40 / T 40.5 TBE , Nike Free RN Running Shoes Women's Blue Black Orange 7.5 Seven 1/2 38.5 EuropeanPuma smash slip on denim Color blue indigo Puma white New with box Free shipping , New VANS Womens Comina Slip On Surf hawaiian VN-0ZTTFQH US W 5.5 - 8.0 TAKSEDC Women Mack Skate Shoe White With Multi-Color US Size 6.5 W FREE SHIPPING NEW , Ryka Deliberate Training Shoes - Women's size 9M - GrayWomen's 9 Born Brown Legato Clogs Less Expensive Flats , Womens Reebok CrossFit Nano 7 Weave Electric Flash Training SIZE 6.5 , NEW Womens NEW BALANCE WL 420 DFD Black Classic Sneakers Shoes , NIKE WMNS WOMEN'S AIR MAX 1 ONE ULTRA SP 789564-001 NIKELAB BLACK WHITE SZ: 10.5 , Nike Women Free TR 6 Running Trainers Training Shoes 833413 500 SZ 8.5 NEW , Nike 654845 001 Women's Air Kaishi Running Shoes Sneakers NEW IN BOX , Propet Washable Walker Walking Shoes, Women's Size 6 N, Blackadidas F10 TRX FG Blue - Womens - Size 8 MWomens Sandals Northside Savannah Sport Sandals Black NEW ,
"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."