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.78NP111171 LSP30 Women's Shoes Size 7 M Bronze Fabric Flats Johnston & Murphy , sperry boat shoes size 7.5 7 1/2 women’s , Spot on F80016 Ladies Pump Canvas Shoe Mustard, Fuchsia or White (R4A) , Rialto Genevieve Ballet Flats Women's Size 8M Black With Bling EUCSAS Three Strap Black Flat Sandals Adjustable Straps Size 7.5 M Ladies Women , Stuart Weitzman Black Nappa Quiltable Flat - Size 7, UsedCLARKS Medora Elie Size 8.5 M Brown Sage Leather Mary Jane Flat Shoes For Women , Sam Edelman Fallon Ballet Flat - Women's Size 9M, Black , Nine West Beachinit Synthetic Womens Ballet Flat- Choose SZ/Color. , Zee Alexis Women's Sammi Woven Mary Jane Shoe Turquoise Multi 8.5 M , Asics Womens US 7.5 GT-1000 Athletic Running Shoes Blue T7A9NWOMENS SAUCONY GRID COHESION 9 WHITE GRAY RUNNING TRAINING SHOES SIZE 7.5M H241Skechers Shape-Ups Shape Ups Women's Walking Fitness Shoes Size 9.5Brooks Twitch S Track Running Shoes Women Size 9 , MERRELL Women's Siren Sport 2 Trail Hiking Shoes Size 8.5 Elephant Pink J58282 , Skechers Women's Double Up - Fairy Dusted,, Light Blue, Size 7.5 hgAISAUCONY Grid Nitro 2 Running Shoes, 6.5 WomensNew New Balance Womens Ww1765ko White/Blue Walking Shoes Size 5.5 (AA) , Brooks 3D Stretch Print Glycerin 14 Women Sneakers Purple Athletic Shoes Sz 9.5 , NEW Nike Womens Air Max 1 Mid Sneakerboot Shoes Boots 8 Pewter/Violet MSRP$120NEW VANS AUTHENTIC LO PRO CITY BLACK TRUE WHITE SHOES WOMENS 6.5 MENS 5 VAULTDIADORA WOMAN CASUAL FREE TIME SNEAKER SHOES CODE CRYPTON NYL 12 156727 , SKECHERS Ladies Flex Appeal 2.0- Sneakers Navy/Pink Sz. 8 M NIB , Skechers BOBS Women's Squad - Alpha Girl Sneaker, - Choose SZ/ColorNIKE Zoom Rival S 8 Track Field Sprint Spike Running Shoes White Blue Women's , FILA RAY Disruptor Fashion Sneakers For Women's Shoes FS1SIA1169X White PrismAdidas Cloudfoam Pure Running Shoe - Womens , Vans ERA 59 Denim C&L Black/Gum Women's Shoes 8 - Men 6.5 , Vans Classic Slip On Velvet Oxblood Black Women's Size: 6.5 , Vintage 1993 Womens Nike Sneakers White Blue Pink Size 9.5, Retro 90’s!
"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."