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.Life Stride Soft System Black Low Heel Loafers Moccasins Shoes Size 8M Buckle , Easyspirit women blue/black all man made materials mary janes flat size 9 , Hot Girls Bowknot School Oxfords Womens comfy Block Heels Loafers Patent Leather , Naturalizer Brittany Flat - Women's Size 8M PinkSuede 3D Embroidery Flats Women Slippers Loafer Pointed Toe Women's ShoesLucky Brand Black Cutout Flats Size 8B.O.C. Born Concepts Margaret Slip-On Comfort Clogs 964, Red, 6 US / 36.5 EUMinnetonka 6 WOMEN BROWN LEATHER COMFORT CASUAL BEACH POOL LAKE SANDAL SHOE~~BETSEY JOHNSON Gold Sparkling DRREW-G Shoes Sz 10 Yellow Brick Road~Satin ties , Zara Women's Pink Jewel Rhinestone Beaded Bow Ballet Flats Shoes Size 6.5New Women's Skechers 49040 Interstellar Intergalactic Shoe - Navy Size 6 (Z2) , SKECHERS TAUPE & PALE PINK EYELET-PATTERNED ATHLETIC SLIP-IN SHOES, 6M, MINT!! , adidas Originals Women's EQT Racing 91, White/White/Turbo Fabric, Size 9.5 , New Minnetonka Womens 622-Brown-5 Brown Casual Shoes Size 5Blue Women Lady ALL STARs Chuck Taylor Ox Low Top classic Canvas Sneakers US8.5 , Spring Step Women's 10 Carmen Loafer Brown Leather Moccasin Toe Slip On Shoe New , Kalso Earth 'Aspire' Brown Leather Ballet Flats Women's 8 B , Clarks Mens Bootie Slippers Size 8.5 (635) , FitKicks Womens Flexible Flats - Active Lifestyle Footwear - for comfort and , New Balance Womens 877 WW877SB Size 7 D Walking Shoes Gray - 1353Womens Nike Free 5.0 Running Shoes Size 7.5 Black Pink Volt 642199 002 , New Balance WW577VK 577 Black Walking Straps Comfort Sneakers Women's US 10.5 2E , WOMEN'S SHOES KITSON L.A.. DECK TENNIS SHOE SZ 7.5 , ASICS Gel Contend 3 Womens Size11 Running Cross training Shoes Navy Pink Y457Converse Womens Size 5 CTAS Madison Ox Thunder/White/Black 559351C2018 Fashion Breathable Ladies Zip Hidden Wedge High Top Board Sneakers Shoes szNike Air Huarache Run Prm Women's Black Light Bone 683818-010 USA Size 5adidas TUBULAR DEFIANT PK - White - Womensadidas Originals BY9847 Womens Campus W Sneaker- Choose SZ/Color.Adidas Tubular Defiant Women's Size 10 Grey Space Dye Core White Mesh Sneaker ,
"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."