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.Womens Driving Loafers Moccasin Oxford Leather Casual Shoes Wedge Slip On ShoesLifeStride Women's Valerie Driving Style Loafer, Black, 6 M USPOLO RALPH LAUREN LILIA 7.5 B Canvas Boat Shoes Blue / Pink Women'sTuk shoes Peacock feather US size 7Muck Boots Breezy Ballet Flat All Purpose for Ladies Women's - Black/GrayBASS ADLEY Women Brown Blunt Square Toe Slip On Loafer Slides Mules Shoe 8M #C24Vintage Dr Martens leather shoes 8547 made in England UK size 3 US womens 5 , BOC Born Women 7.5 Nurse Black Slip On Shoes , Sperry Top-Sider Dunefish Boat Shoes 147, Tan Multi, 9 USNew Antonio Melani Black Calf Hair Slip On Loafers Casual Work Size 8.5 , Tommy Hilfiger Denim Women's Size 5.5M Shoes Athletic Comfort Casual Tennis , Black Suede Edelweiss Loafers Haus Behr US Size 9.5 Euro Size 41 , Reef Women's Rover Low Fashion Sneaker Tobacco 10 MCocorose London Shoes 531716 Black 37Ladies Equity Casual Shoes - BlossomPRADA Women's Black Leather Cushioned Sole Cap Toe Ballerina Flats US 36.5 , Tommy Hilfiger Shoes Women's Size 5 Red White SneakersRealtree OUTFITTERS Camouflage SHOES WOMENS SIZE 4 M COBRA JR.IMAN Runway Chic Luxurious Slip-On Sneaker Padding Trim BLACK 11MDockers Women's Jensa Brown Leather Boat Shoes SIZES! NIB NEWCROCS Sarah Espresso Brown Suede Soft Fuzz Lined Clogs Heels Womens Sz. W10 $129 , Drew Shoe Women's Bloom II Mary Jane - black - 14353-12 - size 8.5 WWJELLYPOP Pink Embroidery Casual Sneaker Women's Size 7 1/2NWOB Women's Adidas Originals Azurine Low Top Pink Animal Print Sneakers Sz 8Ryka Transition Cross Training Dance Fitness Shoes/Sneakers Women's 8M EUCWomen's PRADA Ballerina Flats. Size 6 Practical And Economical Flats , SKECHERS 12656 BKW Skechers Burst 2.0 New Avenues Womens Slip On SneakersNew Nike Fi Flex Golf Shoe Women Size 6 Pure Platinum Racer Pink Blue 849973-001 , ADIDAS DURAMO 8 W BB4671 BLUE WHITE ORIGINALS RUNNING WOMEN'S SIZE 6.5 NEW WOB , Merrell Womens Vapor Glove 2 Black/CastleRock Trail / Hiking Shoes Size 5
"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."