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.DG VENICE WO'S 7.5 W BLACK PRE-OWNEDZHENZEE MOCCASINS BLACK WHITE HOUNDSTOOTH WOOL FOXY ME MOD 9 9.5 L RETRO NEW , Sperry Top Sider Tan Gold Glitter Sparkle Size 9.5 Boat ShoesWanted Shoes Women's Erie Fashion Sneaker, Black, 8.5 M USG.H. Bass Co Women's Siena Black Wedge Loafer 9M , Sidekicks Black Fold Up Ballet Flats Shoe with Zippered Purse Sturdy SoleEASTLAND Womens Brown Leather sandal Shoe Sz 9 Sling Back , COLE HAAN WOMEN'S PINCH LOAFERS PINK 2.5 MEDIUM $80Thierry Rabotin Brown Embossed Lizard Loafer Flats 38.5 8.5MINNETONKA womens FAWN tan leather Moccasin shoes slippers 9.5 , Merrell Jungle Oxford Chocolate Brown Air Cushion Shoes, Women's Size 6EARTH SPIRIT WOMEN LEATHER SHOES BROWN LADIES FLATS SIZES 6 , SOLUDOS Women’s Low Boots, Cream, Size 6 , Women's Ladies Summer New Toe Post Diamante Flower Low Heel Flat Sandals**Clarks Ashland Effie Casual Slip On Shoes - Women's Size 8 M - Black , Adidas Superstar 80’s Retro Women’s Sneakers BZ0642 Black/Off-White Sz 10Nike Women's Air Exceed White Athletic Training Shoes Size 8Skechers Shape Ups Womens sz 9.5 Walking Exercise TENNIS SHOES EXCELLENTDansko Professional womens Brown Mary Jane style clogs Euro 40 US Sz 9.5-10Skechers Tone Ups Fitness Womens Size 7.5 Gray Blue Sneakers Shoes WalkingGrasshoppers Women's Lily Wedge Sneaker Peacoat Navy Size 8.5 IKlTUnder Armour Atlantic Dune T UA Black Men Thong Flip-Flop Sandal 1252506-004 , Forever Link Women's Remy-18 Glitter Sneakers BlueNew Balance WL501HXA Classic Running Grey/Black Women size 7.5Converse Chuck Taylor All Star Ox High Top Unisex Shoes W 10 M 8 Pink 137834F , Women's Brooks Adrenaline GTS 16 running shoes size 8 DWomen's Keds Women's Prestige Fashion Sneaker Serviceable Athletic Shoes , Saucony Kinvara 7 LR Women's Running Shoes US Size 6 NIB S10340-1 Cerise/PurpleVince Camuto Womens BILLENA Low Top Slip On Fashion, Smoke Grey, Size 9.0 pTG8 , Chaco Outcross EVO Free Water Shoes, Women's Size 8.5, Teal ,
"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."