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.Dr. Scholl's New Trust Black Womens Shoes Size 7 M Flats MSRP $39.95 , Vintage Dexter Burgundy Leather Tassel Loafers Women's Size 7 M Made in the USA , ECCO Twist Black Nubuck Suede Snakers Flat Shoes size 40/9.5 , New Womens Ballet Flats Pleated Round-toe Faux-Leather Slip-on Ridge GOALIE-SNew Women Black Distressed Denim Slip On Sneakers Size 10Mossimo Ballet Flats Winter White Women's Size 7KRUSH ELIZA Women Bow Loafers Size 8 BlackWomen's Merrell Primo Breeze II Coral Clogs Size 5 16PKelly & Katie Navy Blue Faux Suede Pointy Toe Ballerina Flat Shoes Size US 8 M , SAS Women's Brown Snake Skin Loafers: 12 Wide In Excellent Condition , Trotters Lamar Slip On Shoes - Women's Size 6N - BlackNWT Sanuk FOLKLORE Off White Multi Color Canvas Flats Shoes Womens 9 MAerosoles Women's Spin Cycle Ballet Flat White Size 10.5 Cid5 , Weejuns Willow Loafers - Women's Size 7.5, WhiteRyka Maroon Leather Mesh MaryJane Slip-on Athletic Sneaker 201083 Women 9.5 / 41Dakota Quad Lite STSP Women's Grey/Black Sneakers 7.5M , Hush Puppies KRIYA Brown Skimmer Ballet Flats Womens Size 5 1/2 MNew! Women's Adidas Samoa Vulc J Black/White SZ 6 C76717 H49KEDS Sz 10 PRESTIGE White WH46200 Women's Casual Leather Sneakers VWomen's Funtasma Women's Gogo Beautiful In Colour Athletic Shoes , Adidas Samoa W Athletic Women's Shoes Size 6.5 , Merrell size 5.5 Chameleon Arc black/silver hiking womens ladies shoes NEW , Reebok Womens Hexaffect Fire VTR MTM Running Shoe- Pick SZ/Color. , WOMEN'S NIKE FREE CONNECT RUNNING SHOE, VOLT/BLACK/WHITE, 843966 700NEW SKECHERS WOMENS GOWALK LITE BREAKOUT SLIP-ON SNEAKERNike LunarSolo Women's Moon Particle/Sand/Vast Grey 4080201Hoka One One Clifton 3 Womens Size US 9 Running Shoes Midnight Blue SpringNike Free RN 2017 Athletic Shoes - Women's Size ? - White , Brooks Ladies 8.5 D Wide (40) Addiction Walker V-Strap Black Leather WalkingSkechers Women's You-Shine Sneaker - Choose SZ/Color ,
"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."