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.ADRIENNE VITTADINI Ballerina Flats Sz 7.5 MSize 7.5 7 1/2 Pretty J - 41 Leather Shoes Great for Everyday Casual & Work Wear , DANSKO PAM Slip On Loafers Brown Leather Shoe 6800457800 WOMENS US 8.5-9 , Stylish Brown Leather Nike Pumps - Size 39 , SKECHERS Microburst It's-My-Life Slip On Shoe - Women's Size 8, Charcoal , LabatoStyle Women’s Casual Leather Loafers Driving Moccasins Flats Shoes Wine...Ladies Havaianas Top Mix Sandal Casual Jelly Holiday Summer Flip Flops All Sizes , Fossil Leather Shoes Women's Size 9.5 M Flats Buckle Shoes Black Slip ons. , Comfort Well By Beacon Women's Stretch-N-Form Navy Blue Slip-On Loafers Size 5 , SALE LADIES CLARKS 'COWLEY FOLLY' GREY/BLUE RIP TAPE CASUAL SHOES , ? adidas PERFORMANCE DURAMO 7 Women's Running Shoes Trainers Sneakers AQ6502 , Lucky Brand Womens Madoz Leather Pointed Toe Slide Flats Brindle Size 8.0 DQlU , Reebok royal ultra pink rose women fashion sneaker size 6.5Skechers Womens - White Running Shoes Size 8 (359365) , Chung Shi Stafild Women 7.5 Max Comfort Step Casual Walking Fitness ShoesNWOB Women's Track Spike Nike Zoom Rival S 8 Track Spike 806558-615 sz 8.5Dr. Scholls Women's White Kellie Therapeutic Shoes - Size 9WBrand New Adidas Shoes HOOPS 2.0 MID DB1226 Black White Women's Size 9SKECHERS SHAPE UP 12371 Resistance Runner Kinetic Silver Pink Black Women Shoe 8 , ASICS Gel Venture 6 Womens Size 9.5 D Black Grey Running Athletic Shoes F3-137NEW! Skechers Women's EMPIRE CONNECTIONS Shoes Navy/White T dz , Seychelles Womens Set Black Fashion Sneaker Size 9.5 (29856)Women's Tory Burch Shoes Size 10 Comfortable Feel Flats , PUMA 36596501 Womens Vikky RG Platform- Choose SZ/Color. , PUMA 19003603 Womens Carson 2 Molded Wn- Choose SZ/Color.White VANS (Bongo) Size 9 Women's Shoes - NEW WHITE OR NEW CUSTOMIZED-REDUCED $ , Aerosoles Women's Drive Along Loafer Bone Combo LeatherASICS GEL-Venture 6 - Green - WomensEUC Women's Salomon Speedcross Pro 3 Size US 9.5 Running Outdoor Hiking Shoe A7 , Nike TRAINING Running Shoes Size 7. ,
"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."