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.Easy Street Women's Genesis Flat, Grey Burnish, 5 M US1368 Aquatalia Sawyer Navy Suede Perforated Slip On Penny Loafers Women Size 6 M , Bass Dune wheat enfield oxford hand painted expresso & tree charms nib sz 9M , Bernie Mev. Bronze Metallic Catwalk Slide On Shoe Ballet Flat Size 38 US 7.Yves Saint Lauren Rive Gauche Red Suede metal caped flats Size 41.5 , KEEN XT 1205 Nubuck Leather Red Mary Jane Walking Hiking Shoes Women's Size 8 , Klogs Kennie Polyurethane Clogs Display Model Shoes White 7 W , LADIES SHOES/FOOTWEAR - Step On Air Vamos shoe white multiJust Cavalli Women's Burgundy Pony Hair Ballet Flats Shoes Sz 6 7 8 9 10 11 , Jeffrey Campbell Black white anchor Leather flats size 9 , LADIES CLARKS LEATHER FLAT SLIP ON BALLET PUMPS SHOES SIZES CANDRA GLARE , NIKE ZOOM TRAINER Black White Running Shoes 324514-011 Womens SIZE 9.5 , Women's Bella Vita Valore Moccasin Loafers , Eastland Womens Crystal Slip-on Loafer NAVY LEATHER SZ 7.5 WIDE NEW DISPLAY 7666 , Dansko Blue Black Marble Swirl Patent Leather Clogs Shoes 40 9.5 10 medical ClogPatagonia Shoes Sneakers Size 6 WomenWomen's k swiss classic pink 6.5 Fashionable Patterns Athletic ShoesWomen's womens athletic shoes size 11 Serviceable Athletic ShoesPuma Creeper Clara Lionel White Women Walking Shoes 9.5 , RIVIERAS for J CREW LORD SLIP-ON SNEAKER PEWTER GOLD SIZE 6.5 Retail $130 SPAINGenuine ON Cloudtec Swiss Engineering Women's Purple Size 6 Running Shoes *READ*Grasshoppers Women's Skylar Espadrille Fashion Sneaker - Choose SZ/Color , PUMA Women's Basket Platform Reset Fashion Sneaker - Choose SZ/ColorNew Balance Women's (7.5) Cushion 410-V4 Black Running Athletic Tennis Shoes USA , ASICS Womens Metrolyte IndigoBlue/Bay/Silver Running Shoes Size 8 (417227)NEW IN BOX WOMEN ADIDAS LITE RUNNER SHOES AQ5824 COLOR : PINK US SIZE : 6.5/38 , Propet W3851 Wash & Wear Slip-On Sneakers - Women's Size 8.5W, BlackSkechers Sport Women's S Ynergy 2.0-Side-Step Wide Fashion Sneaker , REGATTA athletic trail shoes GREAT OUTDOORS X-Ert waterproof hiking UK rare , Skechers Sport Womens Breathe Easy Serendipty Fashion Sneaker- Select SZ/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."