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.SALE WAS NOW Ladies Spot On taupe patent synthetic loafer F9875 , CHAUSSURES MOCASSINS CUIR VITTORIO STYLE BEIGE ET CREME T 35NEW Cole Haan Pink Suede & Brown Leather Driving Loafers Slip-on 7.5 FREE SHIPSkechers Womens EZ Flex Glitzy Glamour 22612 Loafer ShoeWomens Brown Leather Born Slip-on Clogs Mules Shoes Size 8/39 , VANELi Womens stevie Closed Toe Mules, Gold galassia, Size 10.0 ledE , Clarks Neenah Garden Ballet Flats 168, Black, 7.5 US / 38 EUEARTH Origins Vivian Women's Brown Leather Slide Mules Clogs Shoes Size 7 M , Merrell 1 Encore & 1 Topo Moc Pro White size 8.5 M Nursing / Work Shoes ClogsALL BLACK Cutout Mesh Women's Oxford, Beige, Size 6.0 NvTyFranco Sarto Womens scranton Leather Pointed Toe Mules Black su Size 6.0 qph2 , Escarpins Talons Compensés Cuir Souple Gris Taupe DORKING T 39 TRES BON ETATFila Women's Size 7.5 Shoes Athletic Running Walking Exercise Yoga Purple/GrayDANSKO Bennett Black Napa Leather Pump Ankle Booties Shoes Sz 41 US 10.5-11Sperry Topsider Seaside Scale Sneaker- Women's Size 9.5 M, Grey , Skechers Go Yellow Blue Gray Women's Running Shoes 10 Ten Sneakers European 40 , Inov-8 Womens F-Lite 240 Black Walking, Hiking, Trail Shoes Size 9 (290983) , Stubbs Wootton Mens Size 12 Wall Street Collection Black Velvet Smoking SlippersSkechers Size 7 Womens Black Slip On Loafers Memory Foam Lightweight Shoes MeshBROOKS RAVENNA VI 6 white/red/green running/cross training shoes . women's 10 , LEVI'S Women's Stan G Slip-On Comfort Sneakers Black Pick SizeNike Sweet Classic Textile Canvas Women’s Pink Sneakers Shoes 378339 Size 6.5 , Womens MERRELL "Lithe Glove" barefoot running shoes, W 11, Grey Purple , MONTRAIL Women’s FluidFlex Trail Running Hiking Shoes Size 8.5 Black Red , ASICS GEL CONTEND 3 Womens Gray Blue Volt Running/Athletic Shoes Size 7.5 , SAUCONY Wome'ns Running Sneakers Tan Sz. 9 , 554888 641 NEW WOMENS-NIKE-FLYKNIT-LUNAR1 SHOES , VANS Dazie-Hi (Surf Floral) Windsor Wine WOMEN'S Casual Shoes SIZE 10NIKE AIR MAX COMMAND WOMEN`S SHOES TRAINING RUNNING ATHLETIC NEWPure Navy Fringed Leather Slip-On Sneaker, 36
"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."