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.Womens Jack Rogers shoes sz 7.5 M Navy Blue slip ons Slight WedgeSAS Womens Shoes 9.5 Tripad Comfort Black Leather Oxford Rubber Soles Hook Loop , Meltonian Germany Espresso Brown Comfort Slip-On Dress Loafer 7M , Orthofeet 825 Wichita Black Diabetic Therapeutic Shoes Women's Size 7.5 X-Wide , Womens Leopard Sperry Boat Shoes Size 9Dansko 39(8.5-9) Womens Tan Leather Mules Slides Scalloped Trim Comfort EUC , Taryn Rose Calf Hair leather buckle Ballet Flats sz 37 , ARRAY Womens Freedom Leather Square Toe Loafers, Lime, Size 7.5 OrRkJBU by Jambu Design Cordoba Womens 7M Clog Leather Work Shoe Brown Comfort lightHotter comfort concept Womens sandals US 8 , Clarks Evianna Doyle Womens Black Leather Fisherman ShoesWalking Cradles Women's Caden Mule Black 6.5 M US , Asics fuzeX Women's Shoes Size 9.5 , TS shoes TAKING SHAPE sz 7 / 38 Electra Block Heels comfy chic easy-wear NIB!Brooks Vanguard Women’s Running Shoes Sneakers Black Sz US 8 BNike Womens Free TR 6 Black Fitness Trainers Sneakers 12 Medium (B,M) BHFO 6726 , Saucony Womens Trinity Mint/Grey Running Shoes Size 7.5 (358127) , Puma Basket Heart Patent Jr Halogen Blue Lilac 3 4 5 6 SportsLocker 364817-05Reebok Womens Elle Running Shoe- Pick SZ/Color. , Under Armour Women's Kick Sprint Track Spikes Sz 8.5 NEW 1297114-100 Black/WhiteVANS Authentic (Washed Canvas) Dress Blues/Gum Skate Shoes WOMEN'S 8Unicorn Canvas Shoes, High Low, Women Men, Cute Unicorn Lover Gift, Narwhal, CatNike Womens Black Running Shoes Size 10 (29961)Inov-8 Womens F-Lite 250 Blue Running Shoes Size 10 (429808)New Balance Women's Cushioning 620v2 Trail Running Shoe - Choose SZ/Color , SPX Limited edition Shoes Street Slam Hi, Very Kool! Hand Made! , Vans SK8 Hi Slim Leather Canvas Bone True White Women's Size 10 , MBT Sport 02 White Leather Athletic Rocker Walking Shoe Size Womens 7 , Reebok Womens Easy Tone Fitness Shoes White Pink Size 7.5 Smoothfit. , Under Armour Women's Mirror Studiolux Seamed Leggings - Choose SZ/Color ,
"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."