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.New Womens Low Wedge Heel Slip On Metallic Hue Tassled Shimmer Brogue Loafers , Munro Heels Size 9.5 Wide Black Horsebit Stretch Comfort American Shoes WomensDansko~Maroon Leather Mary Janes Shoes~37 (6.5-7)~$130 , Trotters Brown Leather Flats Size 8 1/2 S/Slim 1 3/8" Heels Loafer/Slip on StyleMojari Indian Women Shoes Handmade Leather Sandals Flip-Flops Jutti Clogs US 6 , PG Lite Sunshine Womens Mary Jane Slip on Suede Casual Shoes size 7 Beige , Womens Summit Kamora Shoe Nude Pink Patent Leather Pointed Toe Flats Sz 36 M NEW , Clarks Clogs Brown Leather Slip On Buckle 7 M Barely Worn 70832 , Lucky Brand Plaid Ballet Flats Womens 8.5 NEW , **Nine West Batoka Ballerina Flat - Women's Size 7.5M - Black , Sperry Top-Sider Bluefish Boat Shoe Brown Leather Plaid Fabric 2-Eye Womens 8 M , DC Women’s Trase HI TX SE Black/Red High Top Shoe 7MWOMANS 6.5 SNEAKER BY DC SHOECOUSA , BRISSA-1-99 WOMEN EMBELLISHED HIGH SUEDED BOOTIES ELEGANT TANEasy Street Women's Laurel Flat - Choose SZ/Color , HADLEIGH'S WOMEN'S LOAFER IN CREAM, SIZE 40 , WOMENS DC STUDIO LTZ SKATEBOARDING SHOES BRIGHT ROSE (ROB)PINK , Shop6 2018 Fashion Couples Breathable Sport Sneakers Running Flats Canvas Shoes , Skechers Live Smart Fitness Shoes, Charcoal/Aqua, Womens US Size 10Platform Wedge Womens Sport Sneakers Casual Shoes Hidden High Heel Ankle Boots2019 Women Round Toe Hollow Breathable Wedge Heel Sneaker Casual Shoe Mesh Canva , NWT Skechers Womens Hi-Top Canvas Angel Wings Glitter Bling 7MNEW BALANCE 'WARISRB1' Grey/White RUNNING SHOES - 10.5 / 42.5 , WOMEN'S ASICS GEL GT 2150 RUNNING SHOES SZ 9 39.5 USED T054N GUC SNEAKERS , Adidas Womens Lite Racer CoreBlack/CoreBlack/HazeCoral Running Shoes Size 7.5Women's Tory Burch shoeboxes The King Of Quantity Flats , DANNER WOMEN'S ZIGZAG TRAIL - LOW - HIKING - WATERPROOF GORE-TEXNEW BALANCE W690LZ4 BLUE/PINK RUNNING SHOE WOMENS SIZE 6.5 B(M) US , Sam Edelman E7270M3 Womens Marquette Fashion Sneaker 8- Choose SZ/Color.Women's Nike Max Air Run Lite + Pink / Black Running Sneakers (8) 386515?061 ,
"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."