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.White Mountain Aura Off White & Black Espadrille Studded Slip ons 6.5 SALE , NEW Womens SODA OBJECT Maroon Slip On Loafers Faux Fur Fashion Flats Casual Shoe , Dark Red Leather Loafers with gold accents by VANELI 9 1/2 N , DANSKO CLOGS Women Professional Size 37 Black 6.5 / 7 Shoe. Excellent ConditionAravon New Balance Women's Size 7.5 D Boat Shoes Brown Leather Casual Loafer 197Enzo Angiolini Sahni Turquoise Suede Leather Pointy Studed Ballet Flats , CLARKS Womens Kinzie Leather Closed Toe Loafers, Pewter Leather, Size 7.5 cQZM , EUC COLE HAAN Air Womens Green Leather Slip On Mules Shoes SZ US 10BPropet Women's TravelActiv Slip On Fashion Sneaker, Watermelon Red, 11 N USSanita The Original Danish Clogs Women's size 37/ 6.5-7US Black Leather , New FRENCH CONNECTION Black Leather MAEKO Oxfords 8.5 39 $145 Pointed ToeMUNRO Size 8 AA or Narrow Black Nubuck Mary Jane Ballet Flats Shoes , WOMENS FILS MEMORY FOAM COOL MAX MEMORY CLOAK 3 NEW IN BOX MSRP$75.00Women's Pointed Toe Crystal Buckle Satin Flats Heel Ballerina Shoes Size35-43Sperry Top Sider Women's Gray Leather Suede Mocassin Boat Shoes Size 7.5 MSoftspots Womens Trinidad Leather Closed Toe Loafers, Rust, Size 7.0 HPsKWomens Nine West Shoes Gigantico Perforated Star White Tie Flat 8.5 MSalomon Womens Mesh Water/Running Shoes Sz 7.5 Gray Running Trail w/Contragrip , Black cross trekkers shoes slip resistant size 5 MNWT Women's Size 12 Nine West Denim Thick Soled Fashion SneakersBrand New Women's Sneakers Athletic Tennis Running Walking Training Shoes 5 -10Brooks Dyad 3 White/Silver/Yellow Walking Shoe Womens Size 7BWomen's Mocassin cuir 38 Luxuriant In Design FlatsNEW BALANCE Womens WL520MR Classics Shoe US 7.5 BLACK/GOLD NEW , Puma Sky II High Wedge Sneakers 9 Women's Red White , AVIA A5952WSKP Running Training Athletic Shoes Sneakers Silver Pink Womens 7.5Vans SK8 HI 46 Italian Weave/Pig Suede Teak Women's Shoes 8Skechers Women's You Define EXCELLENCE 14962/NVY Navy Brand NewAsics T664N Gel-Flux 3 Women's Size 9 M Neon Orange/Silver Running Shoes , SKECHERS WOMANS SHOES 46940 SIZE 8.5 BIKER RUNNING TRAINING BROWN TAN LEATHER
"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."