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.Sesto Meucci Women’s Driving slip on mules Shoes Brown Size 9.5 NNaturalizer Womens Beige Canvas Sneaker Shoe NWOB - Size 11MSanuk PAIR O DICE Womens Sidewalk Surfer Slip-On Shoes Size 7 US Print NEW 2017Brinley Co Womens Lena Pointed Toe Ballet Flats, Black, Size 9.0 qdbN , beautiful! EASY SPIRIT baby blue leather slip on comfort walkable loafers 9A , REMONTE DORNDORF MARY JANE STYLE FLORAL EMBROIDED SHOES A MUST SEE BARGAIN SZ 38Jabasic Lady Comfort Slip-on Loafers Hollow Driving Flat Shoes8Brown , Easy Street Women's Holly Mule,Navy,5.5 M USWALDLAUFER Women’s Size 5 1/2 M (35 EUR) Black Suede Mary Jane Casual Shoes , Butterfly Twists Olivia Cream Black Womens Ballerinas Flats ShoesAbeo Rocs Black Bethan Nursing Toning Mary Janes Shoes Woman’s Size 8.5 , Sperry Top-Sider Marion Black Crinkle Pate Women’s Shoes Sz 6 NWBINC International Concepts Womens Caleyy Closed Toe Espadrille Flats, 7.5M , SoftWalk Simba Slip On - Women's Size 11W BlackWomens Shoes White Mountain SURF Flats Loafers Driving Moccasin Aqua , Klogs Vivian Clogs Display Model Shoes Barely 11 M , Womens Walking Running Sports Gym Fitness Athletic Cushioned Sneakers US 5-12 , womens nike shoes size 8.5 preownedBeacon Womens Jeannie Suede Closed Toe Loafers, Fawn, Size 8.0 LKB0Propet Preferred Paige Leather Suede Brown Mary Jane Walking Shoes Size 11MNew! Women's Skechers 11931 D'Lites Fresh Start Walking Shoes - White I67 , SHAKE Women's Breathable Athletic Casual Mesh Running Walking Shoes Lightweight , Nike Gennico women size 9 - black gray silver shoes sneakers womensMERRELL Passage Ventilator boots Wo's 7M Earth BrownTrail Hiking Shoe Vibram , WOMENS PUMA SUEDE CLASSIC in colors BLACK SIZE 6.5New Women's High Top Wedges High Heels Shoes Buckled Casual Sneakers TrainersReebok Women's Classic Royal Nylon Running Shoes in White in Sizes 5 to 12 , New Women's Nike Zoom Rev White Gold Basketball Shoe 897626-107 Sz 10.5 , Puma Platform LUX Women's Size 7, 8, 8.5, 9 Black Gum BrownNike Air Max Thea EM Running Shoes White Blue Green 833887-100 Women's 8.5 B ,
"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."