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 STRUCTURED Women's Brown Leather Mock Toe Loafers Mary Jane Strap 7 Mosr- SHOES WOMAN SZ 6 LOAFER WHITE AND GRAY MOC PENNY SOFT LEATHER 1.5" HEELWomen's Shoes Minnetonka Suede Moccasins Brown Size 5.5 M shoesSALE LADIES SPOT ON POINTED TOE SLINGBACK BOW TRIM CUT OUT DETAIL SHOES F8965SPERRY TOP-SIDER WOMENS CROC PRINT CASUAL WALKING PENNY LOAFERS Size 7MIndian Women Shoes Designer Jutti Handmade Flip-Flops Ballerinas Mojari US 5-10Lucky Brand Bapsee Light Blue Denim Multi Slide Mule Slip On Flat 11 , La Plume Italy Blue Denim Daisy Leather Women's Comfort Sandal Slide Shoe Sz 38 , JOLI BALLERINE TOUT EN CUIR VERNI SOUPLE MARRON "COLORADA" P/39 NEUF/EMBALLEAetrex Womens Mary Jane Flat Shoes Suede leather sz 9 C/DLadies Sam Edelman Rae Dark Silver Metallic Leather Pointy Toe Flats NIBKlogs Vida Women's Clogs Display Model Shoes Black Smooth 8 MConverse Chuck Taylor Womens 8 39 Wonder Women High Tops Sneakers Shoes nqr , DREW PARADE III 9.5M Womens Taupe Orthotic Diabetic Comfort Oxford Sneaker $150NIKE AIR PRESTIGE ll High 334480-015 Metallic Silver & Light Blue Womens SZ 7Etonic Dri-Lite Golf Shoes Green White Leather Womens Size 7.5 , women's Asics Phoenix 8 athletic running walking multicoloured shoes size 10CONVERSE ALL STAR Women's Purple Sneakers Size 7.5 Medium EUC , Asics GEL-EXALT 2 Run Sneakers Women Sz 9.5Reebok Women's Size 10 Running - Walking - Shoes - LQQK!!! , NEW Saucony Running Shoes Ride 8 Red Black S10273-5 Women's 10 M(B) $120 Cushion , Nike Roshe Two Floral Print Womens Sz 6 White Pink Blue Brand New Custom , Fabulicious Womens Chic 08 Ankle-Strap Sandal Clear PVC-Tan/Clear Heeled Sandals , Vans Womens UltraRange Rapid Sneakers Pearl Pink Size 6 NewDwarf Hamster Printed (White) Running Shoes For Women-Free ShippingNike Orive NM Women's Running Shoe 677136 039 Size 9 , Under Armour Women's Ignite VIII Slide Black/Brilliance/White SandalsMBT Tan Beige Leather Adjustable Strap Walking Toning Sneaker Womens 7.5 , Clarks Womens - NavyNubuck Fashion Shoes Size 10 (368409) , Ryka Whisk Walking Running Fitness Athletic Shoes Sneakers Silver Womens 6.5 ,
"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."