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.ALDO Suede Maroon Loafers w/ Silver Rhinestone Decoration - Size 8 , Jeffrey Campbell Black Leather Gold Embelishment Flats Shoes Sz 9 Used Favorite , Salvatore Ferragamo Black Patent Leather Flats Shoes Women's Sz 7 Made in Italy , Apex Women's Lisa Brown Classic Mary Jane Flat Style A331W, Size 7.5W , Clarks Haydn Juniper Brow Suede Gored Mary Janes Shoes Womens 9M Slip On Elastic , Aerosoles Driving Moc Bicycle Toe Loafer Beige Leather Stitched Womens US 11MTsubo Terracotta Orange Suede Honnor Flats Size 6, 6.5 $125Tommy Hilfiger Women's Sonya, Marine, Size 6.5 7UMYJ Crew CECE Suede Slip On Ballet Flats Shoes Size 7M Royal Blue RETAIL $128NEW Zara Women Espadrilles Snow Leopard Print Calf Pony Hair Shoes 41/ 9.5 to 10 , Bernie Mev. Rigged Fly Navy Shimmer Women's Woven Casual Slip On FlatsNEW! dv by Dolce Vita Roselyn Suede High-Top Navy Sneakers - Various Sizes!! , Wicked Road Warrior Womens Loafer Boots Black/Blue Size 8.5 , Audrey Brooke Womens Rina Leather Closed Toe Ballet Flats Blush Size 6.0 DEpA2008 WOMEN’S NIKE DUNK LOW 317813-181 WHITE/ORANGE BLAZE-SHOCK ORG (msrp: $75) , Womens Keen Trail Shoes Size 8 US Brown Leather FantasticNEW BALANCE 556 WHITE BLUE ATHLETIC SHOES Womens Size 7B , Tamaris Eulalia 1-1-23603-20 Sneakers - Women's Size 7.5 - Gray MetallicNike Tanjun Running Shoes, Women's Size 8, BlackSkechers Size 7 Beige Loafers New Womens ShoesLadies Tennis DMX Lite Walking Moving Air Tech Max Cushioning Pink Size 7 MedWomen's Adidas F30 TRX FG Soccer Cleats - Silver/Blue/Green - NIB! , Nike Womens Flex Adapt TR, Wolf Grey/ Black/ Lava Glow, 7 M USNIB WOMENS UNDER ARMOUR W MICRO G PURSUIT TRAINING RUNNING SHOES SZ 9.5 11 , Vans ERA Tonal Gargoyle Women's Shoes 7Nike WMNS Free 4.0 V2 Sports Running Shoes Violet Electric Green Sz 9 511527-53 , Easy Street Women's Passion , Skechers Microburst It's My Life 23310/BKW Black White Brand New In BoxASICS Womens Gel-Game 6 White Running Shoes Size 9 (421541)New Nike 684765 Women's Downshifter 6 Running Shoe sz 7M
"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."