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.BORN brown leather adjustable strap MARY JANES FLATS Comfort shoes 41 9.5 M $79 , Easy Spirit Leather Shoes Slippers Ballerina FlatsTan & Coral Women 9 1/2TS shoes TAKING SHAPE sz 6 /37 Verity Sandal pewter/black flats funky NIB rp$150Giani Bernini Odyesa Memory Foam Ballet Flats, Gray, 6 US Used , crocs Crocs Womens Kadee Graphic W Flat- Select SZ/Color. , Cole Haan "City" Brazilian Black Mule Slip On Shoes Women's Size 7 1/2 (D10230)Keds Glimmer Boat Shoes-Women's size 7.5 Cream , Women Flat Shoes Ballet With Low Heel Metal Pointed Toe Flats Hollow Out ShoesEcco Bouillon Womens Shoes Brown Suede Flats Leather Bow Detail Eur 40 US 9-9.5 , NWOB Free People M4D3 Women's Black Mage Slip-On Sneakers Shoes Size 8 , Born 7 Black Women's Oxford Shoes , Diesel - Vintage Sneaker Shoes // Very RARE // Size 5La Sportiva Akyra Women's Emerald/Mint Trail-Running Shoe 8M , Moccasins Leisure Womens Slip On Fur Furry Round Toe Slip On Flats Shoes WalkingEastland Women's Sunset MLB Angels Boat Shoe, White, 6 M USPlanet Shoes Elate Womens Leather Comfort Flats , LANDS' END Men's 13 Arctic Gray Suede Moc Slippers NIB $50 , Unisex Slippers Boots Pure Sheep Wool 4 5 6 7 8 9 10 11 12 13 Christmas giftSkechers Womens 12414 Empire Game On Black/Multi Walking Shoes Size 8 EUCKeen Women's Presidio Black Shoe 6MVasque Women's Pendulum II Gray Synthetic Mesh Trail Running Shoes Size 7 M , Cole Haan Women's White /Gray Athletic Shoes 7.5 B , Women's New sneakers Shop Athletic ShoesWomen's FASHIONABLE BLUE CASUAL SHOES Wholesale Flats , Skechers Performance Women's Go Walk 4 Interact - Choose SZ/Color , New Balance 758 Silver & Blue Fit Walk Athletic Shoes Womans 6 1/2 B 6.5 NIBMerrell Taupe Suede Moc Slip On Casual Shoes Women's US 8M , CONVERSE WOMEN'S CTAS OX 560644C (WASHED LINEN) ALMOST BLACK , NIKE AIR ZOOM PEGASUS+ 32 CP Coral Orange 6.5 37 EUR, $145 CP , NIKE FREE 5.0 TR FIT 3 WOMENS SZ 6.5 CRIMSON TURQUOISE ATHLETIC RUNNING SHOE EUC
"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."