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 Zip Up Barrado Suede ShoesTS shoes TAKING SHAPE sz 6 /37 Verity Sandal pewter/black flats funky NIB rp$150Born Women's Truitt Leather Slip On Causal Shoe Coral Size 7M , LADIES SPOT ON CRINKLE PATENT SHOES WITH FRINGE/TASSEL (2 COLOURS) F80117 , Schutz Black Leather Calf Hair Pointed Toe Camilla Loafers Size 6B $190SKECHERS Relaxed WASHINGTON 49352 Loafer Womens Size 8 , SAS Siesta Burgundy Leather Slip On Moc Toe Loafers Flats Shoes Womens 8SMERRELL BLACK LEATHER SLIP ON MARY JANES SHOE WOMENS US 7M , Cobb Hill Women's Woven Ballet Flats New Balance Shoes Size 7VANELi SINGER 155002-250 Vaneli Womens Singer Loafer 9(B)- Choose SZ/Color.Trotters Womens simmy Closed Toe Mary Jane Flats, Rust, Size 10.0 , ZIERA sz 43 FF womens black OVATION Leather shoes - Current collection [#F77]Propet Women's Travellite Black Walking Shoe 6W , Nike Women's Free 4.0 V2 Running Sneakers , Sofft Fondah loafer black leather suede 7.5 Med NEWSanuk Women's Pair O Dice Prints Loafer Flat - Choose SZ/Color , Steve Madden Womens jill Closed Toe Mules, Red Multi, Size 6.5LANDS' END Men's 13 Arctic Gray Suede Moc Slippers NIB $50 , Haflinger Grizzly Anke Womens Mens Slippers Clogs Slide Mules Wool Felt MoccasinCHAMPION Women's Blitz Runner Athletic Sneakers Shoes Size 9 Black NEW IN BOX , VANS. Women's or Men's CAMRYN SLIM Casual Canvas HI Shoes. Wom. US 10, 10.5 & 11 , Ladies New Balance Fresh Foam Sz9 Runnng Gym Walking Sneaker Black & Cream Nylon , Women's BROOKS Addiction Walker Walking Shoes Size 9.5 B , Women's Womens Slip On Converse shoe Well-known For Its Fine Quality Flats , RARE NIKE SHOX BLACK PATENT LEATHER RUNNING SHOES WOMEN'S 8.5 NEAR MINT!! , sz 9 New Womens Nike Free TR 7 sneakers Trainer Run Running Shoes 904651-002 , New Vtg REEBOK Womens 9.5 Leather Fitness Walker Walking Spell Out Shoes White , brooks Limited Edition adrenaline gts 12 mens Size 9 , WOMENS ADIDAS NEO CLOUDFOAM SUPER FLEX RUNNING SHOES SZ 6.5 M FOOTBED D8432 , 60% OFF! NEW WOMEN'S PENDULUM II RUNNING SHOE. 7. BLACK OLIVE/MAUVE. ,
"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."