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.Van Eli Vaneli Ladies Peach Suede Flats Shoes Sz 5.5M Made in ItalyNew Women Liliana Krixie1 Pointy Toe Rhinestone Rimmed Platform Spectator Loafer , Propet Sandal Walker Mary Jane T Strap Leather White Womens Shoes Size 9.5 W (D) , REPORT Women's Northwest Brown Suede Floral Embroidered Mary Jane Shoes SZ 8.5 , SPERRY TOP SIDER Women's Size 5 M Boat Shoes Canvas Purple Plum Sequin Loafers , AGL ATTILIO GIUSTI LEOMBRUNI~$335~QUILTED LEATHER~BALLET FLAT SHOES~41.5 , Sperry Top Sider Angelfish Size 11 Boat Shoes Women D125 Dock Leather LoaferButterfly Twist CHRISTINA Fold Up Ballet Flats Shoes NUDE Size 7 M (38) NIBDuluth Trading Company Shoes Leather Clogs 8 , Women's Donald J Pliner Hema Shoes Blue Synthetic Loafer Flats Sz 7.5 M NEW $200SPERRY TOP SIDER A/O Silver Metallic Leather Boat Shoe Size 9 NIB $95 , CLARKS Unstructured Size 8 Brown Leather Ballet Flats ShoesAmalfi By Rangoni Italian Womens Flats 6M Gray Black Slip On Roses Dress Shoe , NEW Nike Jana Star Waffle Track - Yellow/Pink Cleats (Women's Multiple Sizes) , Adidas 109629140 Athletic Shoes Women Size 7 , Steve Madden Womens Slick Silver Fashion Sneakers 9B Medium (B,M) , Asics Gel-Preleus T480N Womens Running Shoes Pink Blue Size 5.5Women's Bobs Skechers Pureflex 2-Knockoutz Gray 31401/GRY With Memory Foam , SPERRY TOP-SIDER "BLUEFISH" LEATHER SHOES LADIES US 7 MED EURO 37.5 NEW , Tony Little Cheeks Womens Fit Body Trainers 3.0 - White US Size 7 NWOBWomen's"NEW BALANCE"Black&Pink COMFORT Tride Sneaker Running Shoes size 9.5 M , Reef Womens Fashion Sneaker- Pick SZ/Color.Women's CHINESE CLOTH LADY'S SLIPPERS/SHOES Clearance Price Flats , Women's Nike Air Zoom Ultra Preowned Tennis Shoe Size 10 , Reebok Womens Hayasu Ultraknit Running Shoe- Pick SZ/Color. , ASICS Gel Game 6 Black Yellow , Womens Skechers Synergy 2.0 Side Step Lightweight Walking Black Sneakers US 6-11Nike Air Zoom Pegasus 33 Athletic Shoes - Women's Size 7.5, Grey/PinkNavy Blue Kangaroo Womens Vintage Style Shoe 9 , Adidas Supercloud Element Refresh W Running Shoes 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."