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.Monroe & Main Trendy Womens Sz 6 M Black White Buckle Flats Spats Loafers Shoes , Anne Klein iFlex Akiota Turquoise ballet Flats eith ruffled toe sz 8.5mASGI WHITE LEATHER UPPER MADE IN CHINA SICE 7.5M , ALLROUNDER Mephisto Mary Jane Beige Mesh/Leather Women’s Comfy Sport Shoe 10 1/2Naturalizer Brittany Round Toe Ballet Flats 964, Taupe , 11 W USMadden Girl Women's Elliss Loafer White Fabric Size 8.0Women's 7 Amalfi by Rangoni Italian Leather Black White Snakeskin Open Toe Flats**SKECHERS Bikers - Mary Jane, Women's Size 8, Black , MUNRO MALLORY BONE BEIGE LEATHER 7 N $200 NIB WOMENS LOAFERS DRESS SHOES M206278 , Ariat Sport Barn Paddock Clogs Leather Size 7.5BLPB ballerines femme ELLA Metal Bronze P37 neuves été 2016HUSH PUPPIES Women's Biege Suede HP 360 Casual Slip On Walking Shoes Sz 6 B3836BROOKS Ravenna 9 Women's Size 6 W Blue Running Training Athletic Shoes X11-556REEBOK size 8.5 womens REFLECTIVE gray & white PT Prime lightweight running shoe , Adam Tucker Womens Nikki Leather Closed Toe Ballet Flats, Tanljg, Size 8.0 iAGyK-Swiss X 160 Heather Cmf Womens Pink Textile Athletic Training Shoes , Womens Asics GT 2150 Running Shoes, Size 9.5 , Nike - Pink/Blue/White Running, Cross Training (Women's 8) - Used100% Authentic Black Sheepskin Slippers Men Wool Shoes Women Australia ScuffSALE @ VIONIC Zen 1st Ray Technology Athletic Sneakers Shoes Womens Sz 9.5 ??b1 , Converse Jack Purcell Womens 6 Polka Dot Jane Ox Blue WhiteWomen's FAGUO Cypress Gris Rose Wear-resisting Athletic Shoes , Hoka One One Women's Challenger ATR 3 Athletic Training Running Shoes Size 8.5VANS Sk8 Hi Slim Ceramic/Parisian Night Teal Skate Shoes WOMEN'S 9.5NIB Women's New Balance Minimus 40 Trainer Shoes WX40MB Wide(D)&Med Width , Brand new leather white Women's Tennis Classic Sneakers Shoes size 6Converse Women's CT AS Shoreline Beach Glass/White Slip On Sneaker-Size size 5VANS Brigata Lite (S&L) Tornado White UltraCush Lightweight MEN'S 6.5 WOMEN'S 8Puma Suede Heart Safari - Tan - WomensMizuno Wave Inspire 10 Running Training Sz W 6 Blue Pink Womens 1A1 ,
"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."