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.LADIES WOMEN FLAT ELASTIC SIDE PLUMPS PLIMSOLLS TRAINERS RUNNING SHOES FROM SIZELucky Brand Womens Size 8.5 Abbee Flats Leather Black Tan Ankle Strap Pointy ToeLadies Spot On Flat Casual Shoes Label F80041 , Clarks Collection Womens 6C Metallic Gold Loafers Fring Tie Accent Comfort EUCSTUART WEITZMAN Brown Leather Loafers Faux Fur Womens SHOES Sz 6 M , MEPHISTO Women's Loafers Air Cooled Brown Leather Slip On Comfort Shoes Size 8.5 , Steve Madden Womens Choppur Closed Toe, Pewter Mul, Size 5.5VINCE CAMUTO LONOVAN Tan Suede Designer Flats Comfort 8.5 M , RALPH LAUREN POLO SPORT Low Ankle Duck Shoes Women's Sz. 5.5 US 36 EUKlogs Piper Womens Clog Shoes Display Model Leather Rosewood Black 8MNB New Balance 692 Black and Blue Women's Mule Tennis Shoes Size 7 NarrowMerrell Willow Chocolate Brown Leather Womens sz 8.5 Slip On Loafers Flats Shoes , Skechers Ghenter Srelt Sneaker - Women's Size 6.5 BlackMadden Girl Everest Women's Black Fashion Shoe 8 Medium , ZOOM RIVAL XC WOMEN'S TRACK SHOE Style 749351-054 MSRP $65 , $58 RYK? Women's 7 M Beige Leather & Mesh Fishermule Slides Tangie ? , New Balance 442 Running Shoe's Women's size 9 WhiteWomens Skechers Shape Ups Running Cross Training Shoes Size 8.5 USSkechers Flex Appeal Love Your Style Womens 8.5M Running Shoe Sneaker 11728 Blue , Women's nike roshe run One Dmb We Have Won Praise From Customers Athletic ShoesWomen's Earth women shoes 8.5B Exquisite (in) Workmanship Flats , Women's teal flat shoes size 10 New Style FlatsFitFlop Women's Gogh Pro Superlight Medical Professional Black Patent Size 5.0Womens ASICS GEL-CUMULUS 14 White Running Trainers T296N0100 , Women's Merrell Pulse II Grey/Blue/lime Leather suede Low Hiking Shoes 7.5 USGerardette's Daughter Print Running Shoe- Free Shipping , Women's adidas Original's Superstar Shoe C77153 White Size 7Taryn Rose Womens Sasha Low Top Slip On Fashion Sneakers Champagne Size 7.0 U9Converse CT Dainty OX Aero Blue Quilted Women Size 6 , LIU JO shoes sz 8.5 Europe 39 black leather. Made in Italy ,
"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."