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.WOMEN'S Monet Victoria Flat Slip Ons GOLD NEW IN BOX DEFECT! SIZE 6.5 MSRP$37Women's Suede Pointy Toe Ballet Flat Shoes Multi-clolored Casual Slip On Loafers , BRAND NEW WOMEN'S BALLERINA BALLET FLAT SHOES - IRISWear. Ever. Eugene Slip On Clogs - Women's Size 8 M, Brown , BCBG Girls Snake Buckle Loafers Slip On SZ 9Skechers Gold Leather Mary Jane Comfort Straps Shoes 21298 Women's US Size 8COLE HAAN MORGAN SLIP ONS BALLET FLATS LEOPARD CANVAS RED TRIM NKE AIR 6 BDANSKO Womens 36 6 Leather Wingtip Clog Oxfords Platform Nurse ShoesOLIVIA K Women's D'orsay Pointed Toe Fashion Ballet Flat Buckle Ankle Strap BM , Womens Prevata Italian Loafers Leather Soles 9.5B Silver , Sanuk BLANCHE Womens Sidewalk Surfer Slip-On Shoes Size 7 Eggshell NEW**Dr. Scholl's Oceana Loafer - Women's Size 8.5W - Brown , NATURALIZER CALE Ladies Brown Square Toe Croc Print Texture Loafer Sz. 10 M NIB , Women's Skechers Mules - Gratis Cloud - Navy - New in Box!!Alex Marie Open Toe Flats Brown Croco Womens Size 9.5 M , NIKE AIR MAX 1 Womens 7 White Silver Purple Athletic Trainers Shoes - 407865 , Women's New Balance 677 Cardio Comfort Gray Running Athletic Sneakers Size 10 B , New Skechers Womens Ez Flex 3.0 Majesty Comfort Memory Foam Shoes , Cole Haan Air Laurel Womens sz 9 B M Patent Leather Penny Loafer Shoes Dark TealDexter Women's Raquel IV Bowling Shoes Size 6.5 Save 40%!!Dunham Hiking Walking Trail White Gray Beige Pull On Shoes Women’s Size 7 BRyka Womens F0180m1 Grey/Lime/White Walking Shoes Size 8.5 (28300) , Excellent Condition "Reebok" Size 7 Women's Running Shoes v68270Reebok Womens All Terrain Freedom Running Shoe- Pick SZ/Color. , Converse All Star Chucks Pink Metallic Low Top Shoes Sz 10 ~*~ NEW no tags L@@KLa Sportiva Synthesis Women's Fjord Hiking Boot 10MASICS GEL-Nimbus 20 Running Shoes - Women's Size 6, Black/Carbon/Whiteadidas Women's Originals Tubular Viral Shoes GG8 Chalk White S75914 Size 7.5 , 23435 Skechers Active EZ Flex 3.0-Songful Womens Slip On- Choose SZ/Color.Women's Nike Roshe LD-1000 Black/Orange/Summit White Sizes 6-11 NIB 819843-005
"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."