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.P24 NEW Attilio Giusti Leombruni Gray Suede Buckle Loafers Women's Sz 36 M , Clarks Bendables Black Leather Womens Shoes Criss Cross Leather Sz 6M NWOTJournee Collection Womens Landry-s Pointed Toe Ballet FlatsDr. Scholl's Black & White Dyed Real Cow Fur Pointed Ballet Flats Shoes Sz 8M , Ladies Clarks artisan "Bright" 6.5M. 72699 pre owned , Women's GAP Silver Gray Mirror Print Flat Shoes Sz 9 / 40Gap Women's Green Perforated Round Toe Slip On Ballet Flats US Size 7.5Merrell Primo Scoop White Leather Slip On Clog Mules Casual Women's Size 11 MLauren Ralph Lauren Imogen Oxfords 294, Black, 5 US / 36 EUReaction by Kenneth Cole Black Athletic Mules Mary Janes Casual Shoes Size 8 M , Klogs Natalie Women's Clogs Display Model Shoes Infield Chaos Brown 8.5 M , Skechers Madison Ave-Urban Glitz Black/ White Womens Sneakers Size 8.5M**Rockport Paulette Casual Slip On Shoes - Women's Size 7.5 W, Black , Sweet Womens New arrival Pointy toe Flats Ankle strap Date Stylish shoes party , Derby en cuir MITICA 32006 BLEU , Nice fashionable shoes! Bzees 8.5W blue and graysReebok M47657 Womens Zquick Dash Athletic Runiing Shoes Solar Yellow Sz 10 , Cole Haan Suede Leather Tassel Loafers Shoes Womens Size 6.5 B Orange ItalyNIB Marc Jacobs Slip-On Sneaker 41 $198 , Merrell Women's Mix Master Move Glide Trail Running Shoe Carbon Size 7M , FitKicks - Women's Breathable Ergonomic Comfort - Non-Slip Sole Active Footwear , SKECHERS Womens D'LITES Biggest Fan Black Casual Athletic Shoes Sz 10 EW F3-814 , Diadora FLAMINGO - Blue - WomensWomen's DANSKIN LEATHER ATHLETIC......SIZE: 7.......EXCELLENT CONDITION Flagship Store Athletic Shoes , Dr. Scholl's Women's Freehand Athletic Shoe White Perf Leather Comfort ShoesASICS GEL-Excite 3 - Grey - WomensNewton Running Boco AT Athletic Sneakers, Women's Size 12, Blue/Yellow NEWPuma Basket Future Minimal Casual Women Shoes - Safety Yellow Metallic LeatherKeds Women's Champion Lurex Fashion SneakerOsiris Skater Shoes, Size 8, Neon Multi Colored, Convoy Mid,
"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."