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.clarks artisan size 10 m black , NEW Women's MUDD FELIX NATURAL Slip On Flats Loafers Dress Shoes SZ 5.5 , ANN KLEIN Womens iflex Brown Loafer Slip On Shoes Size 6.5M , Womens Andrew Stevens Black Leather Camilla Logo Flats Size 6.5 , Women's Enzo Angiolini Black Leather Cross Strap Ballerina Shoes 7.5 M , UNISA Nude Jeweled Flats Accent Slip On Loafers Mules Sz 9.5 EUCSkechers Bobs ~ Kitty Smarts ~ Womens Slip-On Plush Flat Shoes ~ NIB , EARTH ORIGINS EVELYN NAVY BLUE 7M FLATS NEW WITHOUT BOXJ. Crew Brown Patent Leather Ballet Flat Shoes Size 9 1/2 Made in ItalyGrace Womens Flats Slip on Leopard Print Buckle Decor Date Walking Casual ShoesWow! Cole Haan Women's Shoes Collection Prime Brown Suede Buckle Size US 10 DSperry Seacoast Womens STS95129 Navy Casual Shoes Size 6M (X116)Peter Miller Suede Loafers Size 10W , Women's Nike Vapor Court 631713-146 White/ Atomic Pink Tennis Shoe Sz 9 M , Nike Air Jordan Flight Gray & Black Retro High Top Leather Shoe 629942-004 Sz 6Skechers Women's Synergy 2.0 - Mirror Image Ankle-High Training Shoes , VANS New Houston Leila Vault Lady size USA 7 , Converse Women's Chuck Taylor Shoreline Slip Casual Shoe , Skechers? ~ SHAPE-UPS Strength Fitness Shoes ~ 11806 ~ Women Sz 7 ~ VERY GOOD , Womens Trainers Real Suede Lightweight Comfort Casual Memory Foam ShoesPearl Izumi Running Peak II Womens Orange Gray Shoes Size 7 Colorado HikingNew Adidas Womens B39215 CollegiateNavy/MetallicSilver/White Softball CleatsWomens Nike Air Huarache Gladiator QS Fuchsia Glow SZ 6 ( AH7702-500 )New Balance 990V4 Running Sneakers- Training Grey/Castlerock Shoes Women's 8.5 DWomens NIKE FLEX TR 5 black mesh athletic sneakers sz. 7.5, 9.5 $120 , Vans Old Skool Sherpa Turtledove White Women's 8 Skate Shoes New Faux FurASICS Women's Jolt Running Shoes Glacier Grey/Aqua Splash/White Size 9.5Adidas Women's Tubular Invader Strap Shoes Onix/Onix size 9.5 , Heelys 770286 Girl's White And Purple One Wheel Canvas Trainers New , Nike Vandal Low Red White Blue Sneakers Womens Sz 7.5 Hard Rare Color ,
"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."