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.Toni Pons Shoes Espadrille Flats Brown Suede Loafers Size 40LIFESTRIDE SHOES WOMENS SIZE: 6 M , Clarks Womens Size 8.5 Brown Suede Cap Toe Ballet FlatsBORN Leather Mules Shoes Women's" 9 MediumBOC BORN CONCEPT Cognac Brown Leather Slip On Chunky Mules Woman's Sz 9 / 40.5 , Rocket Dog Fran Clogs - Women's Size 10, Black , Women's Barnardo Matrix" Moc Leather Loafer Pewter Color Size 7M (GKBx11Keen Womens 7.5 Shoes Brown Mary Jane Slip On Casual Suede Leather - S1 , Ladies Nine West Black Leather Buckle Flats Worn Once 7.5 M EUC Girl CodeINDIGO by CLARKS CHARLIE BROUGE Oxford, Black, 7.5M US / 5.5 UK / 39 EUNike Air Force 1 07 Women's White Basketball Shoes 315115-112 , Ladies Shoes Wild Sole Surf Multi Coloured Slip On Elastic Casual Sneaker 6-10New Seychelles Snake Printed Leather Pointy Toe Flats Women's Size 7 M* , ADIDAS CrazyMove Studio BB1590 Yoga Dance Training Minimalist Shoe Sz 8.5 REDMERRELL BRINDLE Womens VIBRAM Brown Hiking Shoes Size 8.5 ** EXCELLENT **Nike WMNS Air Force 1 Lo '07 Suede Dark Grey 10.5 special field air force , adidas F10 TRX FG - Black - WomensWomen's American Eagle Outfitters Shoes Diversified Latest Designs FlatsWomen's UNIONBAY Women's Dancer Ballet Flat Exquisite Flats361 Degrees 361-Overstep 2 Black - Womens - Size 6 B , adidas Originals ZX 700 W Black White Palm Tree Womens Casual Shoes AQ3143 , New Balance Women's 711v3 Cross Trainer, Vintage Indigo/White, Size 5.0Skechers Flex Appeal 2.0 Womens running casual 12775/BBK Sz6.5-10 Fast ship LVans Classic Slip On Suede Fleece Black Women's 9.5 Men's 8 Skate Shoes New , Ahnu Pier 3 Casual Sneakers - Women's Size 8.5, Grey/MintWomens ECCO Biom Yak grey/seafoam green walking show size Excellent CondZee Alexis Women's Danielle Woven Fashion Athletic Shoe Red US 6-6.5 NEW , Dolce Vita Oriel Women's Fashion Leather Sneaker shoe - Silver - 8.5M , NIKE AIR PEGASUS `83 KJCRD WOMEN`S SHOES TRAINING RUNNING ATHLETIC NEW , FILA Memory Foam Walking Running Shoe 8 1/2 Medium Width ,
"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."