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.Socofy Sz US 8 EU39 Handmade Leather Slip On Flats Tan Woven Detail Art To WearDonald J Pliner Snakeskin Danie Loafers 7.5 M Women Pink Rhinestone Shoes BrownBorn Women's Raquelle Flat, Natural Crochet, 10 M USLADIES CASUAL SYNTHETIC ANNE MICHELLE SLIP ON NUDE SHOES "L4945"EASYSPIRIT TRAVELTIME NAVY LEATHER/FABRIC SLIDES WOMENS 7.5NClarks Artisan Women's 8M Snake Print Leather Loafers Slip On Flats Shoes #G21Used Mary Janes size 7 Black , Halogen By Nordstrom White Leather Manny Draped Mules Womens Size US 7.5MBoden Alice Flat Navy Purple Aqua Size 7.5 M , Skechers Breathe Easy Good Life Womens Memory Foam Shoes , TOD'S Wine Burgundy Leather Driving Moccasins Loafers Women's US 7G.H. Bass & Co. Navigate Off White Womens Sneakers 10MNike Air Max Black size 6.5 used , Skechers Ladies' Go Step-Lite Black Grey Walking Shoes - Size Varies , SKECHERS GO WALK WALKING SLIP ON WOMEN'S sz 7.5 euc heather gray original , SAUCONY COHESION 4 WOMEN'S RUNNING*CROSS TRAINING SHOES SZ 7 IN VERY GOOD COND.Nature Breeze Womens Shoes Size 6 Trendy FlatForm Black Adams Family (50)Woman Sanuk Yoga Chakra Flip Flop Sandal SWS10577 Black 100% Original Brand New , New Bella Vita Womens Emilie DarkBrownSuede/PlaidFlannel Fashion Shoes Size 7.5PUMA 36616902 Womens Basket Platform Metallic- Choose SZ/Color. , RYKA Ryka Womens Fierce Walking-Shoes- Pick SZ/Color.New Womens Nike Lunarcharge Prm Premium Shoes 923286-500 sz 7 iced lilacRYKA E9726M1 Womens Noomi Running-Shoes- Choose SZ/Color.Middle White Pig Print Christmas Running Shoes For Women-Free Shipping , New Nike Womens Free Rn Run Running Shoes 831509-002 sz 10.5 Triple BlackAhnu AF2473 Womens W Sugarpine Air Mesh Hiking Shoe- Choose SZ/Color. , Women's Adidas CloudFoam SuperFlex - Red - Width: med - RunningWomen’s Mizuno Wave Enigma Running Shoes Size 10.5 ~ GOOD CONDITIONReport Womens Albie Black Vegan Leather Studded Loafer Sneakers Size 6.5 , Women's Nike Free TR Shoe 6 Black ,
"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."