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.BEACON EUROFLEX Women Black Leather Diamond Weave Loafer Mules Shoe 7MJessica Simpson Bart Flats Size 8 , Kenneth Cole Reaction Moccasin Style Loafers 8 1/2 M 8.5 Womens Shoes , **Sam Edelman Felicia Flats - Women's Size 6 M, Black/Gold , BOBS from Skechers 31891 Womens Bobs B-Loved-Sparkle Linen- Choose SZ/Color.BROWNS COUTURE GUM FLATS, RUBBER SOLES, TAGS ON, Sz 7B, HEEL ½ inch, CALF LEATHELucky Brand Womens Red Snakeskin Pattern Mules Size 9 , CLARKS Womens Kinzie Leather Closed Toe Loafers Black Combi Size 7.0 3Tyq , Ladies Patent Shiny Buckle Front Low Heel Silver Gold Trim Women's Flats Shoes , Pin Up Couture Women's Teeze 12-6Sanuk Pick Pocket Plaid Black Vest Shoes , Born Women’s Brown Leather Casual Slip On Shoes Size 8 US $95 , Reebok Easy Tone Smoothfit 55025513 White Walking Athletic Women's US 7New Womens Simple Take On Ribbon Metallic Delphinium Blue Gold Sneaker US 7 EU38 , Women's New Balance White Tennis Shoes Size 10 WW411WT Walking Athletic , WOMENS SNEAKERS SIZE 8.5 DR SCHOLL'S RAVENLanvin $550 Shearling Sneaker Seen on Rihanna Black 36/6 Hi-Top , Skechers Performance Women's Go Walk Lead Memory Foam Slip-On Walking ShoeGra...New Womens Nike Lunarepic FK Shield Gyakusou 859890 400disney evil queens inspired HIGH TOPS HAND PAINTED MADE TO ORDERNEW NIKE AIR ZOOM FEARLESS CITY SHANGHAI TRAINING RUNNING SHOES WOMENS SIZE 12 , Nike Air Max Sequent GS Running Kids Youth Shoes Vivid Purple 724984-501 , New Balance W6073GRG Womens Cush+ Heathered Thong Sandal- Choose SZ/Color. , New Paperplanes Women's K- Max Sports Air Running Athletic Shoes(P1101) Pink , ONEMIX Sweet Women Leisure Shoes High Top Loafers Knit Flats for Walking TravelNike Air Zoom Fitness - Women's 904645 001 size 10 new in the box reg $100.00 , REEBOK Women Shoes Princess Fashion Sneakers White 1475 Athletic Classic , Womens Nike Shox Baby Blue Metallic Running Shoes 392868-040 SZ 8 , Women's Cushe Boots Allpine Tundra Dark Brown/Purple UW01905 Brand New!!! , ZARA HIGH-TOP REAL LEATHER SNEAKERS 2017 SCARF SAND NUDE 39,US8,UK6 REF 7167/101 ,
"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."