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.MERRELL Womens US 8M Angelic Slip On Brown Smooth Leather Wedge Heel ShoeMax Rave Silver/Gray Ballet Flats with Buckle Size 8New Women Betani Abela-7 Faux Suede Pointy Toe d'Orsay Ballerina FlatNEW Women's Causal Web Slip On Round Toe Flat Comfort Sneaker Shoes Size 5 - 10 , Propeet Rejuve Flats Size 7 Wide Tan & Black Houndstooth New In Box Style EMMA , Womens Black Mushroom Brand Shoes adorned with Black Ribbon size 6 1/2WMuk Luks Women's Size 8 Shoes Blue Flower Erin Sport Flats Sling Backs loaferClarks Braided Brown Leather Slip On Plain Toe Mules Shoes 83642 Women’s Sz 7MG.H.BASS Bass Flex Step Nicole MULBERRY Size 6.5 Suede Uppers Women Flat Loafers , Gently Used Betula Boston Taupe Suede Clogs - Size 11 Women - 9 Men , Cole Haan NIKEAIR black patent leather flats Womens US size 8 BHanna Andersson Women Shoe Size 40 9 9.5 Ballet Flats Pastel Leather Toe Cap BowHavaianas Women's Slim Hardware Flip Flops Black UK8 (41/42)MINT BORN WOMEN'S GRAY SUEDE MARY JANE FLAT SHOES SIZE /US 7.5JBU Jambu Designs Wildflower Red Women’s Mary Jane Style Sz 8.5 M , Dr. Scholl's Womens anyway Closed Toe Mules, Black, Size 8.5New Quiksilver Womens Aqys700027-Xswg Shoes Athletic Shoes Size 6CONVERSE ALL STAR CHUCK TAYLOR SHOES SIZE-3 WOMENSMerrell Leather and Textile Slip-on Shoes - Dassie Fold Moc burgundy Size 8.5m , Marc Fisher Barnum Espadrille Sandals 030, Light Natural, 8.5 USSkechers On-The-Go 600-Venture Chocolate Men Sports Sandal Shoes 55366-CHOC , Adidas Womens Terrex Climacool sneakers size 7 Black and whiteNike Classic Cortez Suede Womens AA3839-600 Rose Pink Running Shoes Size 12 , Women's Ellie Women's Fame-601 Reputation First Athletic Shoes , Women's F8812 Ladies Pointed Dolly Shoes Quality Product Flats , Asics JOLT Women's T7K8N.9667 Glacier Grey/Aqua Splash/White Running ShoesPropét Womens Eden Strap Low Top Velcro Running Sneaker White Size 8.0Umberto Raffini Sandals Shoes Snake Print Size 8 Signature Very Gently WornWomen's ADIDAS NEO CLOUDFOAM QT RACER Gray Running Sneakers Shoes AW4313 DEFECTMERRELL Strap Nubuck Leather Sandals Performance Footwear Hike Trek River Sz8 ,
"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."