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.Sperry Top-Sider BLUE SHOES WOMENS SIZE 8 1/2 M , ""YOKI - GABBY - TURQUOIS BLUE, FRINGED SHOES"" - 8 1/2 - HALLOWEEN , PLATFORM OXFORDS WOMEN LIDDY-3-07 ELEGANT BRONZE , Dansko Elisa Women's Slip Resistant Shoes - Size US 7.5 - Red SuedeTALBOTS Women Ballet Flats Size 9AA Black , Eastland Womens Morgan Loafer- Pick SZ/Color.Enzo Angiolini Moc Toe Espadrille Women size 7 m Gold LeatherCOLE HAAN WOMEN'S HINCKLEY BOOTIES (W00381) BLACK SUEDE 5 MEDIUM $280NEW Sperry Women's Bahama 2-Eye Shoes Rose/Cord Sequin Sz 6.5 , Women's Fashion Outdoor Athletic Running Sneakers Casual Walking Sports Shoes , NEW Isaac Mizrahi Live! Sage Black Leather Captoe Ballet Flats Shoes Size 8 M USARIAT Black Leather Horsebit Clogs Mules Slip On Women's Shoes Sz 9.5 B (F5) , Nike In-Season TR 4 Women's Training Sneakers Sz 6 653543-001 Black BlueMen Sanuk You Got My Back II Slipper Canvas SMF1109 Tan 100% Authentic Brand New , SKECHERS WOMENS BURST 2.0 GAME CHANGING FASHION SNEAKERS /WMLTSkechers Shape Ups White Pink Grey 11814 Walking Toning Work Out Shoe Womens 7.5 , Ryka Deliberate Athletic Shoes - Women's Size 9 M, Black/MintWomen's Reebok Astroride Athlux Women Low-priced Athletic ShoesWMNS NIKE LUNARCHARGE ESSENTIAL BLACK/DARK OBSIDIAN-VOLT 923620 007J-41 Women's Duchess Brown KJ15DUC34 SZ 9 EURO 40Nike Women's Zoom Fit Training ShoeAsics Onitsuka Tiger Snowtopia Brown Leather Warm Fur-Lined Winter Boot Women 10 , Creative Recreation Shoes Cesario Lo Red Mesh Sneakers Womens 7NEW PUMA NEO BALLERINA Pink Black Women 7 Dance Fitness , Adidas Originals Flashback - Women's Trace Scarlet/White/Trace Scarlet Size 8 , NEW NIKE DUNK LOW Womens 7 (5.5Y) LTD NIB sb NRNike Free 4.0 Flyknit Running Shoes Womens Size 8.5 Blue Black Fast Shipping , Skechers Originals OG 85 Shoes Womens Memory Foam Retro Athletic Fashion SneakerVintage USA CONVERSE Chuck Taylor Teal Blue Canvas Sneakers Boy's 3.5 / Wmns 5.5Women's Skechers Kiss HAPPY MOMENT 49880/BLK Black Stretch Fit Brand New
"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."