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.Sanuk Ivory Fabric Womens Flats With Khaki Around Heel With Dots. Size 7Crocs Jelly Shoes Ladies Size 11 Black , CROCS Olivia II Wo's 7 Black Ballet Flats Gray Faux Fur InsoleZARA WOMAN SS17 FABRIC MULES REF:3651/201 Size 37 Tweed Mules**Sperry Sayel Away Washed Loafers - Women's Size 8.5, YellowWomens Size 5 Keen "Howser" Burgundy Slip On Loafers Quilted Wool , MERRELL WINTERLUDE WATERPROOF BOOTS WOMENS SZ 6.5 / 37Skechers Gowalk Lite - Coral Natural Womens Boat Shoes Size 7MRed Adjustable Tie Up Sport Soft Sole Casual Women Athletic Running ShoesNew West Loop Womans Flats Size Large 9 10 Black Cream Canvas EspadrillesDANSKO Women's Slip On Shoes Black Leather SZ 39 **L@@K** , Steve Madden Feather Leather Loafers, Women's Size 10M, BlackNew Multicolor Nine West Womens Kyla Flat shoes size 7.5 , Dansko Professional Clog - Women's Size 12W Brown , Franco Sarto Baylor Loafer - Women's Size 9.5 M, Red , Nike Rival XC Running Cleats Gray Synthetic Women8Medium (B, M)**Propet TravelActiv Casual Slip On Shoes - Women's Size 8 2E - BlackBreathable Mesh Sneakers Women Athletic Shoes Sport Flat Outdoor Running CasualFolle de Joie Pink Leather Perforated Slip On Sneakers Size 36.5 , SAS Walk For Life C6923906 Women's Athletic Tripad Comfort Women's US 8Grasshoppers Women's Windham Boat Shoe Stone CanvasASICS T6K7N.9797 Womens Gel-Scram 3 Running-Shoes 9.5 M Carbon/Cosmo Pink , Baskets Femme DC SHOES BRISTOL LE Black Goji Hypra tendances ! , ASICS GEL-190 Trainer - White - WomensA375 Nike Air Max Thea Women's Running Shoes Gray 599409-023 size 8 NEWADIDAS DURAMO 2 G02113 Size: 6 RRP $159 New in Box , NEW ASICS GEL-NIMBUS 12 WOMENS RUNNING SHOES 2A NARROW WIDTHNice White Blue & Silver REEBOK Walking Running Shoes Sz 10 CM 27 , NIKE Zoom Rival M8 Track Field Sprint Running Spike Shoes. Size 7.5 , New Balance Women's T510v3 Trail Runner
"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."