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.7812900 LDF20 Women's Shoes Size 7 M Silver Leather Slip On Johnston & Murphy , SAS Easier Loafers Bone Cream Leather Slip-Ons Comfort Shoes Women's Size 8 MWomen's VINTAGE Cole Haan Loafers Shoes Size 8.5AA Brown Woven Leather AC8DANSKO Sage Green Suede Professional Clogs Comfort Shoes Women's Size: 39 / 8Beira Rio Atlanta Womens Cushioned Active Casual Shoes Made In Brazil , Merrell Plaza Bandeau Cherry Oak Suede Mary Jane Flats, Women's Size 37.5 / 7 , Minnetonka Women's Boat Moc - Black - 7NWT Crocs Women's Sienna Shiny Flat Shoe Oyster Silver Sz 10 White Ballet FlatsARRAY Womens Freedom Leather Square Toe Loafers, Bone, Size 9.5 DcqY , Vogue Womens Grace Flat Faux suede tassel buckle Slip on Casual Driving Shoes SzMerrell Siren Sport Hiking Shoes Women's Size 7 LOVED Used Condition , IKRUSH Women's Amrata Diamante Sliders Size in BLACK Size 3Women's Eeric Javits Squishee Moc Loafer Hickory/Black Braided Fiber Size 7 MLifeStride Women's Gita Slip-on Loafer - Choose SZ/ColorB. O. C. by Born Binta flats grey lizzard 6.5 Med NEWMen Beach Mule Summer Close Toe Flip Flops Laofers Sandals Hollow Slippers Shoes , Womens NIKE Dual Fusion ST2 Size 8.5 Athletic ShoesBROOKS Glycerine 10 Shoes Womans 8.5 Running Training Gray Pink AthleticWomen's Classic Suede Leather Shoes Superior Quality Flats , Women's Nike Classic Cortez SE 902856 006 Metallic Pewter Deep Pewter Snake Skin , New Women's Puma Fierce Velvet Rope - 190347-02 - Pink Training Sneaker , ASH TAUPE SUEDE FLORAL EMBROIDERED SNEAKERS SIZE 36 , Ryka Women's Grafik Flow Cross Trainer, Blue/Pink, 7.5 M US , Converse Size 8 Womens CTAS HI Blue Green Brazil Flag Sneakers New Unisex Shoes , Nike Superflyte Black White Running Shoes Sneakers 916784-001 Women's Size 9.5 MBrooks Cascadia 11 Women's Size 8.5 B Running Shoes Blue Sneakers CarpeLE COQ SPORTIF Deauville Zebra Women's Shoes *All Sizes , Womens White Nike Air Satin 7.5New Puma Suede Women's Blue Sneakers size US 6.5C , Unisex DARK BLUE Leather Authentic Don Ed Hardy 7829 CLUB Series Shoes SIZE 9
"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."