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 WOMEN LOAFERS US SIZE 6.5 M SOLID BLACK LEATHER. , Clarks Artisan Ideo Chilly 7.5M black suede loafers womens flats shoes 66544 , Dexflex Comfort Women's Shoes Size Cream Loafers Slip On moccasinWomens Size 8.5 b.o.c Born Concept Brown Leather Loafers/ClogsED Ellen DeGeneres Aviana Slip On - Women's Size 6M BlackEcco Brown Distressed Leather Oxford Sneakers Shoes womens Size 41 US 10EDDIE BAUER BEIGE LEATHER UPPER MADE IN BRAZIL SIZE 6.5 M , DailyShoes Women's Classic Flats Comfortable Criss Cross Elastic Band Round F...Aravon Betty Women's Casual Shoes - Black ‑ Size 7 D , Tahoe Max Black Grey White JSports Fashion Sneaker , Dansko Professional Black Leather Clog 41 Stapled Clog CollectionDr. MARTENS Women's Size 8 Flower Brown Leather Chunky Oxford Shoes - 12283 , Danskin Now Women's Brown Elastic Closure Tennis Shoes Sneakers Size 6.5 , Skechers Active Casual Shoe, Neutral/Pink, Womens US Size 8 , Avon Navy Blue Slip On Fashion Sneakers 6M New , Chic Women's Slip On Flats Oxfords Cow Leather Point Toe Mules Shoes Ankle Boots , IRON FIST DEATH DANCE PLATFORM WOMENS SIZE 11 , LADIES SHOES/FOOTWEAR - Aerocushion Margret black shoe , ECCO RUNNING SHOE, WOMENS US SIZE 8-8.5 GrayPropet Women's Adelaide Bronco Brown Size 7 2A , Dunlop Mens Amable Luxury Slippers Check Print Warm Soft Lined Indoor Footwear , SKECHERS SN45459 Athletic Womens Size 8 , Women's The North Face Trail Hiking Walking Athletic Shoes Gray Silver Black 7.5 , Adidas Blue Suede Gazelle Originals Casual Shoes Trainers Womens Size US 5M , Hoka One One Huaka Green/Yellow Running Shoes Women's US 7.5 Eur 39 1/3 (L2,10) , New Balance Women's WT410v5 Cushioning Trail Running Shoe, Thunder, 6 B US , Fabulicious Women's Romance 301F White Marabou FurSkechers Women's D'Lites-WATER COLORS 11984 White/Mint Memory Foam Brand New , Nike Women's Size 7 Black/White Air Max Sequent 3 Athletic Running Shoes F1-428 , Skechers Performance Women's Go Walk 4-Gifted Sneaker Black 8.5 W US ,
"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."