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.Aerosoles Womens Awaken Tan Pebble Grain Leather Mary Jane Flats Shoes 9 1/2 M , Size 6 Nine West Pink Reptile Trim Mary Janes , Dingo Fluchos Shoes 38 7.5 Black Loafers Moccasins Slip Slide On Cutout ShoesBORN BROWN LEATHER SLIP ON CLOGS WOMENS SHOE SIZE 8M(US). , Chatties Size 11 X-Large Ladies Fashionable Flats Shoes Blue-SHIPS N 24 HOURS , Baretraps MELANY Flats Bow Shoes Career Black Sz 9 M Medium New Without BoxCole Haan Silver Women’s Ballet Flats, Size 5.5, NWB , Sperry Top Sider Boat Shoes Sz 8 Beige Plaid Leather Moccasins YGI M6-115 , K9 BY Rocket Dog Womans Suede Penny Loafers Size 6 1/2 M Slightly Mismatched , Next brand women's pink faux suede flats, man made materials, 7.5 M, 1/2 in heelWomen's Skechers Relaxed Fit Bikers Pedestrian Slip-on Shoes 48930 BRN , Skechers Seager - Prospect Black Bbk Womens Sneakers Size 8M , Vaneli Mango Slip On - Women's Size 9.5M, BlackStuart Weitzman Ballerina Shoes Flats Size 6.5 36 Women Patent Leather , Nike Dual Fusion Lite Running Shoes, Silver/Pink/Lime, Women's 8.5 , Seychelles Survival Women’s 7.5 Metallic/Gold Slip On Casual Shoes X14-1254PUMA WOMENS PINK WHITE RED SPORT LIFESTYLE 304609-03 DRIFT CAT KADIN SIZE 6 NEW , jiasha Women Running Shoes Lightweight Breathable Mesh Athletic SneakersASICS Womens Gel-Exalt 3 Running Shoe Sneaker Purple Silver Size 11 VGUCWomen's new balance size 9 Surprise Athletic Shoes , SUEDE CLASSIC W VIEUX ROSE BLANCNIKE AIR MAX THEA KJCRD BLACK/CRMSN/WHT WOMEN SIZE 9 NEW 718646 007NEW! ASICS Gel-Fuji Lyte Womens Cross Training Running Shoes Shoe Size US 6.5NEW SKECHERS WOMENS GOWALK LITE BREAKOUT SLIP-ON SNEAKERNike Air Zoom Pegasus 34 Navy/Mint Foam 880560 405 Women's Running Shoes Sz 12 , New Women`s Vionic Fresh Riley Walking Sneakers Shoes 355RILEY MSRP$130NIKE ZOOM SHIFT WOMEN`S SHOES TRAINING RUNNING ATHLETIC NEW SZ 9.5; , Zee Alexis Women's Danielle Woven Fashion Athletic Shoes Gray US 9-9.5Brand New VANS AUTHENTIC CLASSIC CANVAS SHOES Woman Size 6.5 Man Size 5Skechers Womens Go Walk Focus 13677 Slip On Walking Shoe
"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."