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.DUCK HEAD Womens Loafer 10 M Shoe Brown Leather Slip On Wedge Comfort Sneaker , Rampage "Linsey" Brown Leather Beaded Fringed Moccassins Flats Shoes Size 8 VGUC , Sperry’s Women’s Shoes 6 1/2 6.5 Snake Print BoatCLARKS Artisan Red Distressed Leather Slip-ON Mules Shoes Sz 7MCLARKS Unstructured Women's Brown Leather Mary Jane Shoes Size 8 M , NEW Women Outdoor Casual Sneakers Fashion Slip-on Shoes Black 4621 e_C , BARE TRAPS Women US 8M Black Leather Adana Loafer Faux Fur Animal Print AccentKeen Womens Harvest Canvas Mary Jane Shoes Sz 7 M Floral & Stripe ���Sperry Top-Sider Women's BAHAMA Boat Shoes in Chino/Oyster Size 5Born Black Women's Clogs Black leather Very Nice 8 /39 M B72603.. Minimal Wear , SAS Viva 9.5M 91/2 brown womens ladies comfort loafers flats shoes L1631386 , Nina Marielle Ballet Flats, Ballet Pink, 9.5 USSummer Women Flats Cut Out Mesh Running Athletic Trainers Shoes Breathable Size , Women’s Gravasphere Black/Gray/White Memory Foam Insole Slip On Shoes ~ 7 , Black Mens Leather Slippers shoes Size 7 8 9 10 11 12 13 shoes Flip-Flop mulesPropet Women's TravelFit Hi Sneaker, Purple/Silver, 6.5 Wide USWomen's Keds Champion Oxford Sneaker Stylish FlatsNike Women's Air Max Zero Athletic Snickers Running Training Shoes Size US 10 , Adrienn Barna (Ruby) Women's Running Shoe- Free Shipping , Women's REEBOK Crossfit Nano 7.0 Cross Training Sneaker - BD5830 Sz 8.5 USEDWMNS Nike Blazer Spikeless Golf Shoes White Black Oreo SZ ( 818730-100 ) , Baskets Femme ETNIES Kirra Black Pink , Skechers Women's GOrun 600 Flux Running Shoe , Ryka Mallory Outdoor Shoes, Women's Size 11 M, Navy/Black , Vans Style 23 V 2 Tone Leather Metallic Port Royale VN0A38GCMWX Women's Size: 8Keen Terradora Hiking Shoes - Women's Size 9, Scotch/MulchDiadora Kuruka Hip Running Shoe Womens Size 8 Black , MERRELL J52410 WOMEN'S SIREN SPORT 2 BRINDLE HIKING TRAIL SHOES SIZE 8 US , Skechers Nampa-Annod Women's Slip Resistant Electrical Hazard Slip-on Shoe 77236 , Vans SK8 Hi Slim Italian Weave Black/Multi Women's Skate Shoes Size 5
"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."