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.Earth Mary Jane Leather Ballet Shoes Women's Size 6B Brown (tu25) , Naturalizer Natural Soul Amber Womens Black Leather Mule Loafer Shoe-Size MediumShi by Journeys Beige Crochet Floral Flats MISSIE Women's Shoes 5.5Women's Minnetonka Moosehide Brown Leather Moccasins Size 9.5 , Cynthia Vincent Gold Ballet Flats Leather Snake Print Shoes 6.5 M Made In Italy , Skechers Relaxed Fit Bikers Witty Knit Slip On Shoes, Women's Size 7.5, BlackBOC Born Blue Tan Suede Flats Tassel Loafers Women Size 10 MJ Crew Size 7 M Tan Suede Leather Slip On Loafers Shoes For Women Made In ItalyNEW Rockport Atarah Laser Cut Leather Ballet Flats, Women's Size 8.5M, BlackKaepa Cheerful Cheer Shoes Size W5.5SANITA Womens Gold Turquoise Brown Croc Professional Clogs Shoes Sz 37 6.5 , Womens Salomon SCS multi color running trail shoes sz 8Sanuk Womens Donna Hemp Slip Ons Burgundy Size 8 New , MERRELL Plaza Glide size 7.5 brown leather women's Merrell Ortholite Shoes , Asics Running Shoes Silver TN8E9 Womens 7.5 FIT Shoe Stunning Barely Used 39Tretorn Women's Carryfrg7 Sneaker, Light Pink, Size 4.5 , Skechers Mellows Hideout Women's 11 Royal Blue Yellow Active Shoe Sneakers 21594 , Skechers Premium Sport Womens 9 Med Leather 1718 Sneaker Shoes Tan Beige LeatherWomen 2018 Spring Breathable Wedge Heels Sneakers Low Top Loafers Shoes Slip OnNew NIKEiD Soccer Women's Black Nike Logo White Cleats Shoes 598927-993 Sz. 8New Balance KVURGBGP W Wide Black Pink White Kids Running Shoes KVURGBGPW , Sneakers and Athletic Jessica Simpson Farahh Multi Rainbow Dot FabricWMNS NIKE CLASSIC CORTEZ NYLON 749864 310 GHOST GREEN/WHITE - NYLON/SUEDE/MESHGrasshoppers Women's Cleo Wedge Sneaker, Navy, 7.5 M US , 2016 Nike Roshe One Flyknit Volt/White/Total Orange/Black Running Shoes! Size 7NIKE FREE TRANSFORM FLYKNIT WOMEN`SSHOES TRAINING RUNNING ATHLETIC NEWNew Women's Skechers 11930 D'Lites Biggest Fan Athletic Shoes Size 7.5 M (O10)Womens Asics GT II Dark Blue Magenta H593Y-5128VANS New SK8-Hi Slim Embossed Cork Vault Lady size USA 7Vans Authentic MLB Anaheim Angels Red Women's 5.5 Skate Shoes New Baseball ,
"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."