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.RIEKER GREEN NUBUCK LEATHER SLIP-ON SIZE 7 - EXC! , Design Lab Womens Sammy Silver Square Toe Loafers Shoes 7 Medium (B,M) BHFO 7313Fabulous COLE HAAN SLIP-ON LOW engineer style SHOES RUSTIC MULES 7.5BNIB Jeffrey Campbell Orlean Embroidered Red Blue Flat Sandals in size US7MBOC Size 7 Womens Gray Clogs Nursing Shoes Excellent Condition , Jutti Indian Bride Leather Flip-Flops Women Shoes Handmade Oxfords US11 , Villager Liz Claiborne Clogs women's Size 6M Leather slip-on MulesSeychelles Womens Nursery Mule- Pick SZ/Color. , Escarpin FUGITIVE talon bride compensé ballerine sandale moc Cuir 37.NEUF. , SPRING STEP STREETWISE BRONZE LEATHER MARY JANE SHOEs USA SZ 39WWFitflop F-Sporty Uberknit Casual Shoes - Women's Size 10 - Charcoal , FREE FISH Shoes 871329 Pink 36Men Reef Slammed Rover Flip Flop Sandal RF2805 Color Black /Brown 100% Original , New Trooper America Men's Corduroy Slip On SlippersLos Angeles Clippers Team Jersey Indoor/Outdoor Slippers ~ Size MED (9-10) ~NWTNew Women's Sneakers Athletic Tennis Shoes Running Sport Walking Teen Casual , Dr. Scholl's Athletic Gray/Purple Leather WMDS4500000 Sneakers Women's Sz 9 GUCNEW NIKE WOMENS ZOOM FIT BLUE GREEN SNEAKERS TRAINERS RUNNING SHOES SIZE 9 , Skechers Tone Ups 11751 Women White Blue Fitness Sneakers Shoe SZ 8.5M Pre Owned , FILA Memory X-Ridge Women's Athletic Shoes Pink, Blue & Gray - Size 7Converse CT AS Women's Blue Sparkle Checkered Pattern Ox 519227F US Size 8 , New Balance Womens Wl520td DustedPeach Fashion Shoes Size 11 (424668) , Women's SUBLIMES BALLERINES CASTANER T.37 NEUVES!!!!!!!!!!!!!! Strong Resistance To Heat And Hard Wearing FlatsReebok Women's Instalite Pro Hthr SneakerAdidas Adizero Tempo 9 Women's Red Night/Icey Pink/Energy Pink BA8239 Sz 8 NewNIKE WOMEN'S AIR FORCE 1 HI LIB QS SHOES SIZE 8.5 khaki obsidian 706653 300Nike Dualtone Racer Women Sneakers Running Shoes Purple 917682-604 Size US 10 , MOVMT Grandview Navy Blue Size 5.5 US Women's The People's Movement Skate ShoesSALOMEN Speedcross Vario Gore-Tex Trail Running Shoe Women 6.5Vans Era (Leather/Plaid) Rhubarb/Black Classic Skate WOMEN'S Shoes SIZE 8
"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."