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.COLE HAAN WOMAN'S WHITE SLIDES SIZE 8Sperry TopSider Leather Sneakers Womens Wos Red Slip Ons Boat Shoes 8.5 M , J Crew Pointy Toe Flats Size 7.5M Pink Italian Small Heel Shoes Loafers-3897 , New White Mountain Cornelia Womens Heeled Stud Buckle Clogs Size 8M BlacAnne Klein Womens Aricia Closed Toe Slide Flats, Meor , Size 6.0Sperry Top Sider CVO Suede Boat Shoes Women's 6 NIB $70 , BOC Hayden Oxford - Women's Size 9 M, Taupe , Mix No 6 Womens Sarlinas Almond Toe Loafers, Black, Size 9.0 59iIRemonte Doris 47 Slip On - Women's Size US:10 / EU:42, BlackLucky Brand Women's Sequin Geo Print Elisabeta Ballet Flats Size 5.5M , Clarks Jocolin Vista Loafers - Women's Size 7.5M, Black/Tan , LADIES LASER-CUT SLINGBACK ESPADRILLE WEDGES 6, 6.5,7,7.5,8,8.5,9,10 , Hot Womens Wedge Heel Peep Toe Sneakers High Top Buckle Strappy Platform Shoes , SAUCONY Cohesion 4 Running Shoes Silver Pink and White Womens Size 8.5 , NEW WMNS NIKE PRESTIGE 3 SKINNY HIGH SZ 9.5 PINK/GREY/WHT CASUAL 551649 661 , Woman's Nike 487788 Gray Split Toe Adhesive Strap Mary Jane Sneakers Size 8 EUCBROOKS "ADDICTION WALKER" women's 6N white leather linear platform walking shoes , Propet Stability Walker Women's White Leather Shock Absorbing Walking Shoes 10 W , Merrell Crush Glove Pink Women's Running Athletic Shoes Size 9.5Skechers Shape-Ups Women's Masai Walking Toning Shaping Shoes - Size 7.5RARE Womens Nike Shoes Blazer Mid Aloha Floral Print in SIze 6.5 , SKECHERS Women's Go Step Lite Slip On Walking Shoes sz 11 Black Suede BlackoutNew SUPERGA 2750 Cotu Classic - Light Grey-Full White , Z-COIL Sneakers Women's Size 8 Pain Relief Therapy Walking Shoes , NIKE WOMEN'S FLEX EXPERIENCE RN 4 RUNNING SHOES SIZE 9.5Adidas ATLANTA Marathon Trainers Running Shoes Wms sz 8 40 EUR Cream Turquoise , VANS ISO 1.5 Wind Chime True White UltraCush Trainer WOMEN'S Size 5.5 , New Balance Womens 590 Running Shoes-Women's Size 8M Grey/PinkPRADA Authentic Sneakers Tan leather Women Shoes Size 38New Balance Women's WT510V3 Trail Running Shoe Size 6.5 Medium
"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."