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.new womens faded glory pink skin print cut out ballet flats shoes size 9 1/2FADED GLORY SHOES WOMEN'S SIZE 7New Women Wild Diva Carson-01B Canvas Pointy Toe Ballet Flat , Elle Womens Celeste Silver Ballet Flats Size 8 BlingI LOVE COMFORT HEART WOMEN'S Brown LEATHER SLIP ON LOAFERS SHOES SIZE 8 MALEGRIA -FEL-714 SNAKE-SKIN GREEN WOMENS MARY JANES SIZE 39Dansko Black Leather Slip On Mule Clogs Size 38 US 7.5 - 8 , $135 Josef Seibel 38 7M red maroon burgundy suede loafers womens flats 21410Marc Joseph Grand Central Dress Ballet Flats, Navy, 5.5 US / 35.5 EU DisplayWomens Athletic Sneakers Outdoor Casual Breathable Running Sports Shoes Trainers , US women shoes Bridal Flats Wedding shoes IndianDesignershoes Khussa juti DD607O , Woman Shoes Paul Mayer Ballet Flat Leopard Red Leather Patent ToeCap 6.5 Size , ASICS GEL-VENTURE 4 RUNNING SHOES - MULTI COLOR ( SIZE 9.5 ) WOMEN`SSkechers Shape-Ups Walking Shoes 11803 Womens Size 9.5 White Blue Silver(B-8 )Pearl Izumi W EM Road N 0 V2 Running Shoe, Aqua Mint/White, Women SZ 8.5 , Womens Knitted Hollow Out Med Hidden Heels Breathable Sneaker Leisure Trainers , New Steve Madden Mens Navy Moccasin Slippers Size 10 , Asics GelFlux 3 (T664N) Running Shoe-Women's Size 9 Gray/Enamel Blue/White , NIKE SHOT CALLER Free Trainer Athletic Women's Shoes Size 7 , New Balance Womens Black Running Shoes Size 7.5 (267176)WOMENS NEW BALANCE 571 TRAIL RUNNING SHOES SZ 7.5 37 B USED WT571GN HIKING XC , New! Women's Skechers 14335 Go Step: Chic Walking Shoes - SIZE 6.5 Black O63New Balance WW928TN Walking Shoes Tan Leather Womens Sz 9D (33-11) , Nike Womens Free TR Fit 4 Running Shoe Sz 7.5 Black Blue Orange ExcellentWomen's Predictions Women's Saddle Oxford Various Styles Flats , adidas CAMPUS - Green - WomensJESSICA SIMPSON 'FITT-SHOOTING STAR' Warm Up Active Ladies Sneaker Sz. 8.5M NIB , Adidas BB1915 Women Terrex voyager outdoor shoes black white sneakersWomen's New Balance 574 Woven Classic Running Shoes - Size US 6.5Converse Chuck Taylor Women's Size 5 M Orange Purple Canvas Shoe Sneaker NIB ,
"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."