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.GUESS Black Gray Tweed Loafers Flats Slip On Espadrilles Women's Size 6.5MCoolers Ladies Flip Flops Pink & Black Sizes 5/6 7/8 Free Post 2 PAIRS , STEVE MADDEN BRICE Women's Multi-color Woven Wicker Stretch Shoes:9.5M US/40.5EU , Cynthia Rowley Womens Paprika Flat Ballet Tyra Suede Pointed Toe Shoes 9 1/2 , Bruno Melli Two Womens shoes black size 9.5 , Keds Adult Graphite Black & Silver Metallic Flats Sneaker Shoes Sneaker Sz 8.5SLOGGERS WOMEN'S GARDEN MIDSUMMER BLACK STEP-IN WATERPROOF SHOE , Clarks 66739 Womens Shoe Size 10M Burgundy Leather Mary Janes Pumps Shoes i7 , New Ladies Women Green Fiber Upper Low Heel Casual Brogue Shoes Office Work Size , Propet Café' (W3205) Womens 10M Mary Jane Comfort Shoes Black Leather U79 , Naturalizer Womens Manor Black Fashion Sneakers Shoes 8 Medium (B,M) BHFO 6929 , Nike Ladies 6/36.5 Zoom Winflo Running Trainers DynamicWeb Athletic SneakersWomens Lightweight Fashion Cool Stylish Comfortable Breathable TrainersAttilio Giusti Leombruni Size 40 U.S. 10 Red Patent Leather Straw Penny LoaferAravon Women's Revsmart Oxford, Black, (Size 8.5 W) , NWT WOMEN'S VANS SK8-HI REISSU NATIVE EMBROAIDERY SNEAKERS/SHOES.SZE 7.NEW 2018 , Brooks Ravenna Womens Size 6.5 Running Walking Sneakers Shoes Blue/Pink (3G)Women's Saucony Ride 7 Gore Tex running shoes sneakers size 9.5Women's Sketchers LightWeight Neon Pink Black Sneaker Shoe Sz. 8.5Size 13 M By Susina Slip on Sneaker StyleRhinestones Women Pumps Platfrom Leather Sneaker Hot Sport Round Toe Shoes ZCY80new balance 998 made in usa 10 Ivory Turquoise Blue New Sneakers ClassicSteve Madden Deylin Gray Microsuee Embellish Slip On Flatform Sneakers 6.5 NEWNike Air Max- Green And Coral- Size 8 , Geox Respira Hi Top Sneakers Purple Patent Leather Sz 36 EU / 6 US / 4 Juniors , Cole Haan Womens Ignatiasam Low Top Slip On Fashion Sneakers Grey Size 6.0 , ASICS Womens - Green Running Shoes Size 6.5 (361711) , REEBOK Freestyle Hi 25th Anniversary Ed. Give a Dog a Bone SZ 7.5 (RK212)Ariat Women's Fuse Athletic Shoe - Choose SZ/Color , New Balance Womens 999 Blue Athletic Shoes Sneakers 12 Medium (B,M) BHFO 4062 ,
"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."