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.Sperry Topsider White & Tan Canvas Boat Shoes - Womens 8 , MERRELL Women's Brown Tetra Sprite Saddle Slip-On Mary Jane Shoe Size 8 , Naturalizer Womens Mina Fabric Almond Toe Loafers, whiskey, Size 10.0 QHFgSPERRY TOP SIDER Womens SEACOAST Green Striped Canvas Fashion Sneakers Size 6.5 , SPERRY TOP-SIDER "AUDREY WOVEN" BOAT SHOES 7M PINK LEATHER , Yosi Samra MAYA Cross Over Ankle Strap Ballet Flats #MA10910 BLACK 6 M NIBLadies Black COMFORT PLUS PREDICTIONS Flats AUS Size 10 WWomen's NATURALIZER Black Leather JACOBA Slip-On Loafers Shoes 7M Ladies $75 , AGL Attilio Giusti Leombruni Womens Black Leather Toe Cap Ballet Flats Size 38 MWOMEN'S KANGAROOS SNEAKER SHOES SIZE 7 BLACK WITH POCKET , Nine West Womens Simily Leather Pointed Toe Ballet Flats, Black, Size 8.5 QYIr , Womens 7.5 M jambu capri brown leather suede clogs shoes booties faux fur wedge , ASICS GEL CONTEND 2 WOMENS RUNNING SHOES....Size 9Skechers Women's Air Cooled Memory Foam Slip On Athletic Shoes Sz 5.5 M D7939 , Skechers Premium Sneaker- Women's Size 8.5, White , Puma Womens Carson 2 Metallic Blue Running Shoes 6.5 Medium (B,M) BHFO 1888NEW! Skechers Women's GO Flex Walk Unfold Slip On Gray 14010 I27adidas response lt - Blue - Womens , Asics Gel-Venture 4 Trail Running Hiking Women's Shoes Grey Purple Black Sz 11Nike Air Zoom Strong 2 Women's running shoes 921335 005 Multiple sizesSkechers 73539 Street Womens Side Street-Studded Quarter Fashion , Nomad Women's Puddles Boot Navy/Red Gingham WaterproofConverse All Star Chuck Taylor Sneakers Black Sequin Mens 11 Womens 13 Shoes , ASICS Womens Gel Kayano23 Silver Running Shoes Size 7 (351623)New Balance 860v7 Womens US 6 Running Shoes, Sky Blue, W860WB7 , SHOES ADIDAS HOOPS MID 2.0 K- B75743VANS Authentic (Vintage Floral) Navy/Marshmallow Skate Shoes WOMEN'S 6.5 , Saucony Kinvara 5 Women's Running Shoes (Size 6) Blue/Slime S10238-3 , Women's Puma Basket Platform Core 364040?02 Puma Black Shoes Sneakers Size 9 , Under Armour Sneakers Lightweight Black Pink Womens Size 10 Athletic Shoes ,
"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."