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.WOMEN'S EASY GOING-LEATHER TASSEL LOAFER-GENTLE WEDGE-COMFORT INSOLE-6W-NWOT , Women's Clark's 31058 Shoes sz.10 M , ENZO ANGIOLINI SHIANA Black Suede Designer Pointed MISMate Flats L 8 R 7.5BOC Born Concept Women's Ballet Fats Size 9.5M Peach Floral Casual Shoes , Mad Love Women's Multi-Colored Textile Slip On Ballet Flat Shoes US Size 11C Wonder Blue suede " Evil Eye " flats.Size 6M. New without box.Womens Rockport Black Leather Casual Fashion Flats Loafers Shoes SZ 6 AdipreneYosi Samra Vera Flats - Women's Size 6, BlackAravon Beaumont Fisherman Sandals - Women's Size 8.5 (2E), StoneAndre Assous Shoes Sandals Wedge Heel Patent Leather Black Size 8.5 US 39 EUR , J CREW Cece Flat Ballet Silver Metallic 10 Slip On Round Toe Ballerina Shoe , Madden Girl Womens Comicc Fabric Round Toe Loafers Black/ Fabr Size 9.0 NU4H , SAS S.A.S. women's comfort roamer shoeWomen's Spiked Studded High Top Sneakers FOREVER 21 Beige, Rear Zipper,Solid M. , Sperry Womens Top Sider Boat White Blue Perforated 9 M Shoes R2 - S 5 , KEDS CASUAL ATHLETIC SHOES CANVAS / MULTI COLOR ( SIZE 8 ) WOMEN’SFree Lance p 36 derbys Rock bleus effet "used" , Nice ECCO Green Faux Lizard & White Golf Leather Shoes Sz 9-9.5 US 40 EURCONVERSE ALL STAR STRIPED CANVAS LOW TOP WOMENS 5.5 MULTICOLOR CHUCK TAYLOR EUCMERRELL Payette J073739 Wo's 6.5 Elephant Pink Sneaker Cross Trainer AthleticReebok Ul 6000 Casual Women's Shoes , VIONIC AGILE FYN BLACK US WOMEN'S SIZES , K-Swiss Women's Hoke SP CMF Sneaker - Choose SZ/ColorSkechers Performance Womens Go Run-Mojo Running Shoe- Pick SZ/Color. , Puma Tazon 6 Wide FM - White - Womens , VANS ISO 1.5 Mono Ivy Green UltraCush Trainer Women's Shoes Size 8 , Saucony Triumph ISO Running Shoes Lavender/Gray Women's US 7 (F2,9) , Demonia Women's Charade 28NIKE WOMEN'S AIR FORCE 1 HI PRM SHOES metallic silver string 654440 002Reebok Classic Princess Sneakers Shoes Womens 9 White Low Ankle Tennis Walking ,
"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."