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.3 Color Narrow Toe Netting and Bowknot Décor with Cushioned Womens Ballet FlatsLadies Spot On Sparkle Dolly Shoes UK Sizes 3-8 F80116 , Trotters Womens Liz Gold Leather Woven Slip On Loafers Flats Size 11M BrazilLucky Brand Ballet Flats Womens Size 6 Shoes , **Bandolino Eritto Flats - Women's Size 5M - BlackReaction by Kenneth Cole Black Athletic Mules Mary Janes Casual Shoes Size 8 MCloudsteppers by Clark's Size 7.5. NEW , SE BOUTIQUE Magenta / Pink Snake leather ballet 7 1/2 USA 38 EURO , Hush Puppies Women's Reo Aida Beige Leather Slippers (5648144) , Skechers Seager - Prospect Black Bbk Womens Sneakers Size 6Mcarino Shoes 968010 BrownｘMulticolor 24ｃｍMarc Fisher Stormy2 Pointed-Toe Flats 804, Black, 8 USNIKE Dart VI WOMENS RUNNING SHOES SIZE 8.5 Pink White Silver 318801-161Converse All Star Chuck Taylor Shoes Size 7 Women's PRISTINE !!! , Merrell Barefoot Access Arc 4 Running Shoes SZ 7 37.5 Algiers Pilot teal purpleNew HOT Women's Running Trainers Walking Shock Sport Lightweight Sneakers ShoesASkechers BOBS Women's Squad-Total Glam Sneaker - Choose SZ/ColorPropet Womens Eden White Walking Shoes Size 8 (AA,N) (19760) , Adidas Womens Size 8.5 X 17.4 Messi FG Shattered Black Red Soccer Cleats NewNew Balance 690 Women's Shoes Size 7.5 Running Athletic Mesh Grey BlueRyka Womens Skywalk Blue Purple Walking Memory Foam Gym Shoes Sz 6 , NEW Montrail Womens Fluidfeel ST Cushioned Running Shoe Size 5.5Madden Girl Women's Bailey-K Sneaker - Choose SZ/ColorNike Ladies Air Pegasus+ 29 Shield Running Shoes ( 536943-406 ) 8USNew women Puma Black-Limepunch Avid Fenty by Rihanna Sneakers Authentic Size 9.5Hoka One Womens Size 9 Tracer 2 Road Running Shoes Pink Purple , New Balance Women's 247 Shoes Black with Off WhiteEasy Spirit Romy White Multi Womens Sneakers Size 9N , NEW ROXY FLAMENCO HIGH TOP SNEAKER SHOES WOMENS 10 CREAM WOVEN FREE SHIP!NEW SKECHERS MEMORY FOAM Women's White Slip On Shoes Size 10 ,
"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."