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.Sam Edelman Jessa Leopard Brown Black Espadrille Loafers Flats 6.5 RARETorrid PU Suede Black Ballet Flats Slip On Shoes Size Women's 12 , Womens T-Strap EVA Lightweight Holiday Open Toe Beach Sandals Flip FlopsStuart Weitzman Womens Brown Suede Loafers Tassels Comfort Size 8 MediumOLIVIA K Women's D'orsay Pointed Toe Fashion Ballet Flat Buckle Ankle Strap BMLadies Shoes Zip up Black or Red Casual Comfort Shoe Cherry Better Size 5-10Rocket Dog Women's Gray Metallic Leather Ballet Flats Size-7 , Talbots 5.5 Shoes Slip On Flats Slide On Tassel Brown LeatherGirls Ballet Flats Silver N Gold Unique Flats Reversible New Size 40 Size 8.5-9NAOT "FLORENCE" Black Leather Clogs Mules Casual Slip On Woman’s Size 41/10U S Polo Assn Comfort Foam Womens Slip On Blue Size 7 Canvas Suede Like Loafer , RARES NIKE ROSE ET BLANCHES CUIR T 36,5 TBE A ACH IMM FP RED MOND RELAY VOIR , COLLECTOR BASKETS REEBOK ROSES BLANCHES T 36 A ACH IMMFP RED MOND RELAY VOIRClarks Women's Sillian Free ClogHalogen Leigh Black Leather Perforated Platform Wedge Sneaker Womens Size 7 MKeds Kickstart Sneaker- Women's Size 5.5, WhiteRed Suede Driving Shoes Size US10 Great Condition.02-3154 Women Asics T7E8N 9701 Gel Nitrofuze 2 Carbon/White Running SZ 8.5Vans Suede Port Royale Sk8 Hi Moc Fringe Merlot Burgundy Red ShoesNew Bobs Sketchers Winter Women Memory Foam Line Faux Fur Brown Cable Knit 5Womens Saucony Cohesion 10 Gray Running Shoes Size 9.5W (C806) , Women's Cole Haan sneakers women shoes Online Athletic ShoesASICS Dynaflyte 2 - Blue - WomensWOMENS FINN GERMANY LEATHER SNEAKERS SZ 42 USA 10 M USED GUC READ , NIKE Women's or mens Size 8 Black Golf Shoes Max Air Stinger cleats , NEW Vans SK8 Hi Top Leather Slim Zip Shoes Unisex Womens Wind Chime Gray 5.5 6 , New Women`s Vionic Fresh Riley Walking Sneakers Shoes 355RILEY MSRP$130 , Women Nike Air Max Torch 4 Running Shoes Size 5.5 White Grey Black 343851 007 , Nine West Women Romancing Blue Synthetic Leather Wedge High Heel Shoe Size 8.5Saucony Hurricane ISO 2 Womens Size 9.5 Blue/Silver/Citron Running Shoes ZU-480 ,
"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."