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.Natural soul espadrilles- Size 8 1/2MARC JOSEPH New York black glazed leather slides, horsebit detail, size 6-1/2M , Bernie Mev Didi Slip On Mary Jane Flats Blue Shoes Women's SizeClarks Keesha Luca Black Patent Croc Print Leather Loafers Shoe Soft Cushion 9.5Børn LADIES BROWN LEATHER UPPER INNER LINING BROWN CASUAL CAREER SHOES SIZE 9M M , FITFLOP 37 7 DUE Ballet Low Platform Taupe Canvas Beige Comfort Casual EUCMILWAUKEE "DESIREE" leather motorcycle/biker riding mule/boot/clog 38 women's 7 , CLARKS Womens Kinzie Leather Closed Toe Loafers, Black Combi, Size 11.0 ZnQJSoft Style by Hush Puppies Womens Pleats B With U Dark Brown Shoe H701216 9.5 WPleaser Pink Label Womens Anna02/b-Bpu Ballet Flat 9- Pick SZ/Color.Ladies Easy B Black / Bronze / Navy Leather Shoes Orlando , Sam Edelman Francis Flats-Women's size 9 M Nude , Q45 Vince Varin Two Tone Leather Plaster/Denim White Leather Sneaker Sz 11 MVINTAGE FOOT JOY Womens Size 7 W Golf Shoes Metal SpikeDenver Hayes Victoria Slip-On Women's Indigo Canvas Shoes 6MSKECHERS Empress - Let's Be Real Casual Shoes, Women's Size 7.5, Grey , Funny Fruit Creeper Shoes Platform Pumps Shoes Ankle Boot Sneakers For Women New , J-41 Wos Shoes AQUARIUS US 6 M Green Vegan Mesh Walking Hiking Hook Loop 234Womens Mizuno Wave Inspire 12 Running Training Shoes Pink...Size 8 , New Balance Women's MD500v5 Spike Shoes Black with PinkEarth Shoes Pomelo Khaki Leather Sneakers Tie Shoes Womens 7B EUCWomens BROOKS Ghost 8 Purple Blue Running Shoes Size 8 US 39 EUR BNEW Women's Asics Gel 160TR White / Lightning / Lavender Leather Athletic Shoes , J Crew SeaVees? Legend sneakers in flannel gray sz 8 NEWVans Old Skool Velvet Gray Black Women's 8 Men's 6.5 Skate Shoes New , Adidas Neo Courtset Womens Suede Tennis Sneakers CG5820 Size 7.5 Gray White , Superga Cotu classic women’s sneakers shoes 8 grey canvas 39 natural casual 2750Ryka Strata Walk Walking Fitness Athletic Shoes Sneakers Black Pink Womens 10 , NIKE [325064-062] Blazer Mid Black/Pink/White?Valentines? Women's Size 7 *EUC* , Saucony Shadow 500 Women's Shoes Size 12 ,
"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."