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.New DV/Dolce Vita Women's KYLIE Perforated Nubuck Slip-On Oxford Flats 9.5 Sand , Women's New Embroidered Ballet Ballerina Loafers Flat Dance Dolly Shoes Sz 6-10G.H. Bass & Co Melinda Women's Black Slip-On Clog 9.5MORTHOFEET Women Horse Bit Loafers Size 6EE Black LeatherEASTLAND ROSY WOMENS LEATHER BOAT SHOES BLUE 8 MTrotters Tan Loafers Size 9.5 S Slim ~Woven LeatherCole Haan Womans 7.5B Olive Leather Luxary LoafersClark's Black Leather Sneakers Running Shoes Size 7USLadies Padders Casual Extra Wide Fitting Shoes Style Daisy -W , Adrianna Papell Size 6.5 M Linda Flats Black Leather Loafers New Womens Shoes , Sam Edelman Felicia Flats Womens Size 8-Black , BORN Size 7 Black Leather Cap Toe Ballet Flats Shoes 38Ivanka Trump Zarina Black Sude Women’s Flats Size 8.5 M , NEW Dansko Womens 37 / 6.5 - 7 Black Brown Leather Mules Clogs $135CLARKS Women's Grasp Chime Slip-On Loafer Black/Black Patent Size 6.5 0R1GNew 3D print Fashion Casual Shoes Women leather Shoes Leisure Comfortable GreenVans Boylston Women Black Textile Ankle Fashion Sneakers US Shoe Size 10.5TOMMY HILFIGER Frank 3 Slip On Sneakers Fashion Mule Flat Slides White Size 7.5Madden Girl Everest Women's Black Fashion Shoe 8 Medium , Nike Air Max 180 + Running Shoes, Glacier Green/White, Womens US 7Converse Pink Textile Women9Medium (B, M) , New Balance 491 Running Shoe Size 6.5 Wide Womens Walking Pink White Grey , LIZ CLAIBORNE Warwick Sneakers Womens Size 10 Olive Green Shoes Gold AccentsPropet Women's Ridge Walker Low Hiking Shoe , Flexus by Spring Step Women's Tinty SneakerHi-Tec V-LITE HURRICANE EVENT Pale Gray Green Trail Hiking Shoes Women's - NEW , Reebok Ziglite Running Shoes Avon Breast Cancer Crusade Women's 8 Gray PinkWMN'S PUMA FIERCE VARSITY 190757 03 TOREADOR BRAND NEW DEADSTOCK , Candies Hardee Womens Fashion Wedge Sneakers Assorted Sizes Brand NewECCO BIOM NATURAL MOTION WOMENS RUNNING SHOES SIZE 40 US 9-9.5 BLACK PURPLE ,
"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."