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.New Womens Fringe Front Bow Fur Lining Bow Moccasin Oxford Loafer Slipper Shoes , LifeStride Women's Azalea Flat, Blackdm, 7 W USRose Petals by Walking Cradles Womens Size 6.5M Brown Shoes Loafers box76Nine West Women's Guinup Linen Oxford Flat , Indigo Rd. Womens Hestley Closed Toe Loafers Black Size 8.0 ZBGJ , L'Artiste Sherbet By Spring Step Black Leather Shoes 36 EU / 6 US WomenNEW Luck Brand Women’s Leather Casual/Sleeper Shoes Size 10 Cream Color , Tahari Womens Gene Tan Raffia Fashion Sneakers Athletic 7 Medium (B,M) BHFO 9111 , BareTraps Kiah Shoe Womens size 7M-Pewter MeshSkechers Womens Size 8 GoWalk 3 Black White Casual Slip On Walking Shoes ZV-1268Diadora DA8AMS5890 Black White Grey Men Slip On Water Sports Sandals Shoes , Womens Size 8 New Balance 80 Runners White/dark grey/purple WE80GP1 , ** Nike Darwin Athletic Sneakers, Women's Size 9.5, Burgundy (Damaged)Skechers D'Lites Biggest Fan Athletic Sneakers, Women's Size 10EW, Navy/White , Cole Haan womens sneakers shoes 7.5 oxfords wingtip black suede pink Lunargrand , Women's Franco Sarto Women's Bocca Loafer Complete In Specifications Flats , New Nike Womens Free RN Flyknit 2017 Run Running Shoes 880844-100 sz 12 White , Earth Origins By Earth Carly Nubuck Leather/Mesh Slip-On Shoes Women Size 12 NEWReebok Classic Leather Clean Exotics V68797 Women's SZ 10.5BNIB ADIDAS ORIGINALS SUPERSTAR SLIP-ON WOMENS SHOES BB2118 SOLAR PINK , Rialto Women's Campari Espadrille Wedge Dusty Rose Metallic Polyurethane , Converse One Star Womens Metallic Leopard Print Low Top Sz 9.5 V2A , Women Adidas Pure boost DPR Running shoes white sneakers 8 , adidas Originals Women's Campus Stitch and Turn W - Choose SZ/ColorNIKE Legend Women SS High LE 333891-001 Black Leather Quilted Boots SZ 8K-Swiss Hoke Fantasy SDE CMF Shoes Black/White/Gold Women's Sz 6.5M Memory foam , Women’s NIKE SHOX 488312-146 White/Teal/Pink Sneakers Size 8 (CON16)Brooks Womens Mach 16 Purple Track Spike Running Shoes 120168 1B 553 Size 6 , Skechers Women's Breathe Easy-Modern Day Charcoal 23013/CCL With Memory FoamSuperga 2750 Cotu Classic Casual Sneakers, Blue
"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."