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.Born Mary Janes Loafer Slip On Brown Leather Strap Womens Shoes Size US 8MReport Signature Sphinx Slip On Flats, Women's - Size 9, Black/WhiteSergio Valente Vintage 80's Denim Jean Pumps Shoes w/ deco zipper Women's Sz 10 , NWT Express Caramel Brown Rounded Closed Toe Bow Trim Ballet Flat Flats 7.5 8Trotters Women's Arnello Ballet Flat, Navy Crocodile, Size 10.0 YvadTommy Hilfiger twprep leather shoes size 7M , Hardrig E 100% Leather Upper (Women's) Size U. S 9 / Euro 39 Flat Black Shoe , SANUK LULEP SAND NATURAL WOMEN SHOES CHESTNUT US 7 , FitFlop Superskate in Velvet Shoes, Women's Size 10, Black (REPAIR)Minnetonka Womens twill junior trapper Closed Toe, Silver, Size 7.0 NJZnGiuseppe Zanotti Silver Metallic Ballet Shoes - 36 1/2 , Easy Street Women's Kacey Flat, Navy/Flannel, 6.5 N USCLARKS Womens Kinzie Leather Closed Toe Loafers, Pewter Leather, Size 11.0 JmggTempur-Pedic Arlow Slippers, Men's Size 10 2E, CharcoalNEW BALANCE 474 TRAIL WOMENS 8 SHOESSketchers Shape Ups 12320 Pink Gray Blue Leather Womens Size 7 , FIla Women's Quadrix Running Shoe (1281) Black/Metallic Silver Size 9Adidas Women’s Fit Foam 3D Cushion Silver/Pink Running Shoes Size 8.5 $85Bzees Cloud Technology White Ruby Sporty Slip-on Skimmer Shoe 8 SaleWomen's Nike Shox 303862 Running Shoes Sz US 7 White Grey Navy , Women's Fabulicious Women's Lip 108 Clear/Clear Practical And Economical Athletic ShoesWomen's adidas Adipower Weightlift Cross Trainer Elegant Appearance Athletic Shoes , Chaco J104958 Size 8.5 Black'Outcross Evo 1' XOXO Hiking Water Shoes For Women , Jambu Women's JBU Pristine SlingbackVANS New Camden Hi Zip Isle Vault Lady size USA 7Wmns Nike Flex 2016 RN Run Pink Black Womens Running Shoes Trainers 830751-600Vans SK8 Hi Slim Zip Iridescent Eyelets Suede Leather Black Blue Shoe Women 9.5 , New Inov-8 Womens F-Lite 235 Running Shoes , Mizuno Wave Evo Cursoris Pink Black Yellow Trainer Running Shoes Women's Size 8STEVEN by Steve Madden Womens Kenner Leather Low Top Slip On, Black, Size 10.0 ,
"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."