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.LAMO Womens akira Fabric Closed Toe, Blue/White, Size 6.0 Ur28 , SKECHERS "Tuscany" Tan Leather Slip On Loafers w/Memory Foam Insoles - Size 9.5 , Life Stride Women's Flats SZ 6.5W , Terrific! Women's Brown L.L. Bean Leather Clogs, Sz 41Olukai Lino Women's Leaf/Leaf Leather Flats 6M , Easy Spirit Aranza Faux Suede Mary Janes, Women's - Size 10 N, Black , BEAUTIFUL 8.5 BETSEY JOHNSON FLATS BLACK SUEDE &LEOPARD SLIP ON COCOH , PROPET Travelactiv SS Mesh Sandals WST003M Blue ~ size 8.5 2E (X) ~ NWB $55Womens Studded Chunky Chelsea Biker Rocker Ladies Flat Ankle Boot Shoe Size , Women's LL Bean Boat Shoes Sneakers Size 11W Wide Blue Denim White Casual W15 , langou Women's Slip On Loafers Casual Flat Espadrilles Platform Pearl Suede D...Indigo Rd. Genetic2 Ankle Strap Ballet Flats, Gold, 6.5 US , Donald Pliner Shoe 6 Ulka Black Leather Patent Bicycle Toe Zip Loafer Italy , Pearl Izumi (Sz 10.0) EM Road N3 Running Shoe -Women's TurquoisePatricia Green Margo Tri Color Woven Leather Flats Size 9 Black White Red , Nike Flyknit Lunar 2 Running Shoes Womens Size 9.5 Pink Athletic SneakersCozy Fuzzy Wool Fleece Memory Foam Slip Men Slippers S Clog Shoes House OutdoorNike Max Air Tailwind 7 Neutral Ride Soft Sneakers Size 10 Black & Pinkwomens asics size 6.5 Running Shoes Used , WOMEN'S PUMA VIKKY PLATFORM SHOE Sz 8.5 BLACK GOLD Patent LEATHER SNEAKERS NEW , Womens Saucony Excursion TR Gray Running Shoes Size 8M (Z733) , New! Women's Skechers Equalizer True Form Athletic Shoe 11891 - Black/Purple E7 , Women's Montrail Rogue Racer Women's 7 Complete In Specifications Athletic ShoesFuntasma Women's Gogo 150 Ankle Boot Black Stretch Polyurethane Ankle BootsMatrix sneakers ," Lady gone rogue fashion!" , Spring Step Brown Sandals Women's Shoes Size 10.5 , Nike Dunk High 6.0 Womens Pink,Gray,Black,Tweed Sneakers 342257-011 , Brooks Women's 'Chariot' Sneaker MESAROSE-FRENCHROAST Size 7 US 38 EURSkechers Women's Size 8.5 D'Lites D'Liteful Tan Gray Athletic Sneakers ZV-1237Nine West Onosha Slip On Sneakers - Women's Size 7M, Gray/Yellow
"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."