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.Indian Traditional Red Flat Sandal Women's Handmade Ethnic Ladies Ethnic SlipperEasy Street Womens Campus Leather Closed Toe, Black, Size 7.0 PFNkDIMMI, REST BALLET FLAT, WOMENS, BLUE, US SIZE 8.5 M, CANVAS/LEATHER, NEW , Ahnu KARMA Lthr Slip On Flats Shoes Mary Jane Sandals Cross Straps Womens 6 NWOBJ.CREW Women's Pink Suede Ballet Flats Size 7 M**B.O.C. Peggy Clogs, Women's Size 8.5 M, BlackCOLE HAAN Brown Driving Shoes Tan Leather Moccasins Loafers women's 8 aaAttilio Giusti Leombruni Women's Beige Satin Cap Toe Ballet Flats SizeBirkenstock Footprints Chestnut Brown Leather Brogue Slip On Comfort Shoe, EU39 , @12 14 Womens Oxfords Crystal Beads Bow Backless Loafer Mule Slide Slipper Shoes , New Womens Skechers GoRun 400 Running Shoe Style 14351 Navy/White 123i pr , FILA Gray Black Pink Leather Mesh Athletic Sneakers Women Shoes Sz 9.5M EUC , Rocket Dog Women's Madox Orchard Canvas Cotton Fashion Sneaker Natural 11 M US , U.S. Polo Assn..(Women's Malory-K Oxford Flat - Choose SZ/Color , New Balance Men's CLASSIC 574'S silver mint moonbeam ML574OUCNew Olukai 20271 DEDE Pehuea Trench Blue Women's Slip On Shoes 6 US , Nike Womens Hyperdunk TB () Shoes Silver Blue Size 13 New , Adidas Originals Equipment Support 93 Nuude Womens Trainers White S76702 M17ASICS Alpine XT Women's Trail Running Shoe Sneaker Gray Sulfer Size 8.5 NEW BOX , Skechers Womens Mark Nason Los Angels Reptile Cup Jett Navy Blue Velvet ShoesNWT Women's adidas Kanadia 7 Tr Athletic Running Shoes B40587NIKE WOMENS LUNARTEMPO 2 RUNNING SHOE , adidas AltaSport CF K Black White Strap Kid Junior Youth Shoes Sneakers BA7459adidas Cloudfoam One Thong Women's Trace Scarlet/Chalk Coral CG2807Asics GT-2000 5 Women's Running US 5, Diva Blue/White/Aqua Splash, T757N-4301NIKE 367193 111 Women's Hyperize Black/White/Silver Shoes , Size US 10, , Nike Dunk Hi LX Python Shoes Max Orange Electrolime Snake SZ 5 ( 881233-800 ) , Salomon Ellipse Women's Thyme Hiking Shoe 7MGRAY VEGAN / TEXTILE TIE-STYLE PHYSIOLOGICAL WALKING EXERCISE SHOES 9.5 / 40 EU , New Balance Womens - Black Running Shoes Size 10.5 (C,D,W) (429949)
"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."