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 J76336 Barrado Leather Mocha Wo's 9 Brown Suede Front Zip ShoeWomen Flat Shoes Fashion Spike Studded Rhinestone Design Casual Slip On Style , NEW London flag blue white red magazine print Moccasin Loafer flat Shoes Sz 6Libby Edelman, Caitlyn Slip-on, dark Mauve Size 7.5 M , Down To Earth Ladies Mule Sandals F10397 Silver (R2A)SAS Women's 7.5N Narrow Leather Penny Loafer Black Slip On Moc Soft Step , Handcrafted Womens BORN Brown Leather Casual 1.5" Heel Oxfords Shoes 8.5N - EUC , Women's Steve Madden Evrest Black Flat Slip On Loafers - Size 9BUFFALO BONEHEAD BALLET FLATS 37 NEW RARITY skull slipper canvas slip on , US 10 Women's Sweet Summer Beaded Sandals ClipToe Flat Ethnic Sandals HH209 , Womens Cobb Hill Shoes Paulette Navy Medium Width Size Comfort $100 Retail , Brooks Brothers Women's Penny Loafers Sz 5 Black Reptile Print Slip-Ons 5 , Fergie Womens Nickel Leather Closed Toe Slide Flats Sand-dune Size 6.5 , Women's Casual Sports Running Shoes Outdoor Sneakers Breathable Athletic MeshNaturalizer Black Leather Mules Slip Ons Backless Slides Size 9.5 NarrowFlat Nine West Saige Natural Multi , GEOX Quilted Tie Front High Top Sneakers SZ US 6 , 02-1417 Skechers Women's Microburst Dearest Sneaker SIZE 10 , New Merrell Womens Ceylon Sport Castlerock Running Shoes Size 5.5 , Women Running Shoes AIR Balance Casual Athletic Gym Sport Ladies ABW91121 New , Womens NIKE Rosherun Winter 685286 660 Team Red Platinum ROSHE Size 6Women's New Balance 991 Grey Suede W991GR Running Shoes SZ US 9 2A , New! Women's Skechers 11793 Synergy Loving Life Slip-On Sneakers - Black N48Nike Roshe Two Womens Running Black White 844929 001 New Sneakers , NEW WOMENS NIKE AIR MAX DESTINY TB SHOES BLACK / WHITE SIZE 7.5Nike Roshe One JCRD BHM QS Sz 5 Women's Black White Red Jacqaurd 1 836230 001Adidas Shoes Arianna Cloudfoam CG2844 Black Silver Womens 6.5 Sneakers Trainers , New Balance WW877 Walking Shoes, Women's Size 12 D, Grey/Light BluePuma Phenom White - Womens - Size 8.5 B , Bobs Sport by Skechers Swift Simple Thread Womens Gray Athletic Sneakers Shoes
"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."