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.LAGUNA WATER SHOES WOMENS SIZE 10SPERRY TOP SIDER 4 J CREW Hot Pink Canvas Loafers Boat Deck Shoe Women Sz 7 �b2Naturalizer Women’s Tan Nude Beige Size 6 Grace Bow Ballet Flats ShoesHelle Comfort By Romu Loafers Brown Croc Print Zip Womens Shoes US 8.5TEVA KIRU T 6086 Womens Leather + Wool Slip On Shoes 9MIvanka Trump Red Suede Leather Pointed Toe Kitten Heel bow Flats 6 Catrina WorkRoper American Beauty Stars And Stripes Slip On Sneaker Shoes Women's US 9/ , AGL ATTILIO GIUSTI LEOMBRUNI FLATS WOMENS BROWN SHOES SIZE 37.5/7-7.5 , COLE HAAN pebbled leather tassel loafers mocassins ivory off white shoes 7.5 B , Eastland 3180 Women's Leather Slip On Loafers Size 9w BrownClarks CloudSteppers Sillian Bella Mary Jane Flats 033, Black, 6.5 US / 37 EU , **Altra Footwear One 2.5 Running Shoes - Women's Size 6.5, Black/Gray/White , Grasshoppers Womens Windham Closed Toe Loafers, Stone, Size 6.5 UNbWADIDAS SIZE 6 WOMEN'S BASEBALL SHOES NEW EXCELSIORNEW Puma Ladies' Leather Shoe Smash Perf Met Black/Gold,Select a Size , Skechers Sport Women's Burst Divergent Demi Boot Sneaker High Top BlkGrey 6.5 , Puma Womens Carson 2 Metallic Blue Running Shoes 7 Medium (B,M) BHFO 2264Nike Anodyne DS Aqua / Pink / Silver Running Shoes 537681-010 Women's Size 10.5 , SAUCONY RIDE FIVE SHOES ATHLETIC WOM'S RUNNING CROSS TRAINGNING GRAY/BLUE 10.5 , Women's Coldwater Creek Women's Wedge Sandals Economy Flats , Pin Up Couture Women's Siren 03 Slide Teal/Pink Faux Leather Platform Sandals , (511882-111) WOMEN'S NIKE ROSHE ONE WHITE/WHITEWomen's Nike Tanjun White/White Sneakers 812655-110 Size 6.5 NIB! NEW , Skechers Performance Women's Go Joy 15601 Wide Walking ShoeBlack/White8 W US13082 Black White Floral D'lites Skechers shoes Women Sporty Memory Foam Sneaker , PLDM by Palladium Women's Gaetane TWL Cayenne 93396-615 Brand New in Box , Nike Air Max Invigor Print Sneaker, Women's Size 8, GreyVans Sk8 Hi Slim Zip (Iridescent Eyelets) Black- Women's 5.5 , Nike Mini Canvas Fashion Sneaker Sz 6Under Armour UA Women Micro G Turquoise Shoes size 10 excellent cond
"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."