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.Amalfi by Rangoni Black Leather Heeled Loafer Shoes Size 9 B US Excellent Italy , Womens Cotton Mary Jane Shoes Ballerina Ballet Flats Shoes 15 Colors , Material Girl Sexy Size 9 Black Platform Bling Rhinestone Heel Shoes Club DanceKunsto Women's Leather Loafer Shoes Slip On US Size 7 Black-Hollow OutBOC BY BORN black leather platform clogs with heel strap size 10 L@@K!BOBS by Skechers Black Tweed Fabric Memory Foam Flats Shoe 33729 Size 6.5 BalletMerrell Dassie Backle Black Women’s Shoes Size 5.5 M , Women's Sperry Top-Sider Bluefish Black Boat Shoes Sizes 5-7Minnetonka Women's Grey Suede Mocs Slip On Shoes Size 7 Leather Loafers , Calvin Klein Leather Women’s Shows Flats Loafers White. Size 8.5 , Corkys Women's Woven Mary Jane Style Flats Liz Bright Multi Size 9Hogl 4-10 1516 Women's Formal Black Slip On Suedette Low Heel Bar Loafers New , Vintage Nike Air Prestige White & Purple Low Top Athletic Shoes Women's 7.5New Fashion Women's Slip On Casual Pointy Toe Faux Leather New Loafer ShoesLADIES SHOES/FOOTWEAR -Cherry Shoes Surprise black , adidas Sunlina - Yellow - Womens , New Balance 578 Classic Women's Athletic Shoes Size 8B (W578GCS)Nike Flex Trainer 7 Women’s Sz 10 White Training Athletic Sneaker Shoes F4-389Vintage Nike Athletic Running Shoes Sneakers 80s Womens 6 Dead Stock Original 85 , New Women's Maxstar 020 Hidden Heel Cotton Tennis Shoes Fashion SneakersCONVERSE Chuck Taylor Womens CTAS HI 559863C Pale Coral Navy Egret Size 7Women's Running Shoe New Balance 890 Multicolor W890WB6 Size 6.5-10 NEW , Adidas Zx Flux W Wide Women's Shoes Size 10women's shoes D.A.T.E. ( date ) 6,5 () sneakers blue silver textile BX59-37PaperPlanes Women Casual High-Heeled Sneakers Taller Insole Shoes 713 CA , RARE Nike Free 5.0 TR Fit 5 Women US 8.5 704695-016 Green Glow Training Shoes A5Womens 10/40 Skechers Active Flex Slip On Running Walking Athletic Shoes 22162 , New Balance 412 Womens Sz 9 M Running Walking Athletic Shoes Gray (G3)Skechers Women's Flex Appeal 2.0 Insights Sneaker /WSL White/Silver Medium , Puma Platform Trace - Black - Womens
"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."