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.Original MOLA Womens Mary Jane Shoes Handcrafted S. America Imported Sz 5.5XHILARATION BROWN & BEIGE FLORAL SLIP ON SHOE-TARGET BRAND SZ 7 TENNIS SHOE �Vince Camuto Black Suede Laser Cut Lancaster Loafers Size 7 MediumNEW WOMENS LADIES CASUAL LEATHER INSOLE LOAFER PUMPS BOAT SHOES SIZE 3-8 , Easy Spirit Esdillona Women's Brown Leather Stretch Loafers Shoes Size 6 1/2 MWOMENS TORY BURCH BEACHER ESPADRILLES FLAT CANVAS TWO TONE SHOES SZ 8Clarks Bendables NIKKI TOWN Brown Classic Oxfords Shoes Women's - NEW - 38523 , Acorn Men's Fave Gore MN - Grey Ragg Wool - XLCole Haan Dark Brown Leather Pumps 8.5 BNike Prime Hype df 2016 - Women size 8Saucony Women's Kilkenny XC5 Flat Racing Shoe, 5 M US, Vizi Orange/Citron , **Puma Match Basic Athletic Shoe - Women's Size 5.5, White/GreyWomens Retro Chinese Style Embroidery Floral Hidden Heels Sneakers Shoes SZ E391 , New! Womens Skechers 11910 Agility Saving Grace Athletic Shoes Grey/Aqua I14Nike Air Max International Shoes 553441-176 Women Size 11 , ASICS GT-1000 6 Running Shoes-Women's size 5 Seashell PinkHot Women’s Salomon Speedcross 4 Athletic Running Sports Outdoor Hiking ShoesTeva Omnium 2 Women Sz 4 Water Shoes , Women's Women’s Adidas Tubular Shoes Quality Primacy Athletic Shoes , CONVERSE All Star Hi Perf RoseReebok Club Memt W Smoky Volcano/Rose Gold/Violet Womens Running Size 9MRare Reebok Classic 903 Womens Size 7 High Top Tennis Shoes Sneakers Hip HopKeds Women's Champion Original Canvas Sneaker White 8 M USVolley Hi Leap Women's Blue/Pink Sneakers 8MVionic Womens 7.5 335 Tourney Sneakers Athletic Shoe Pink Purple Leopard 9004 , Skechers Women's Go Step Lite - Quaint Casual Shoe , adidas BB3487 Women Supernova Running Shoes Sz 8 US , Women's Converse Chuck Taylor All Star Tweed Shoes Women's Size 8 Black & WhiteDC Womens Chelsea TX SE- Pick SZ/Color. , Coral Sonoma Goods Life Leather Ballet Flats Leather 6.5 M Pink Shoes 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."