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.Women's navy leather upper SPERRY TOP-SIDER slip on boat shoes , sz 8.5 M , Women's Mstyle Animal Print Ballet Flats Size 8 , WHITE MOUNTAIN Womens' IAN Black Synthetic Flats Size US 7M (01-W18434SM)CLARKS BENDABLES Ella Celtic 60487 Wo's 8.5M Pewter Leather Wedge SandalsCole Haan Womens 7.5AA Loafers Italian Brown Genuine Leather Low Heels ShoesLucky Brand Emmie Round Toe Ballet Flats 929, Sable, 9 US / 39 EUSplendid - Jerrie Black Suede Ballerina Flat - 8.5M - NEW $98 , Klogs Women's Clogs Display Model Shoes Natalie Micro Puff 11 MLadies Clarks Casual Shoes Tri Step , Born Toby II Clogs-Women's size 6 M SharkSALE LADIES CLARKS 'COWLEY FOLLY' GREY/BLUE RIP TAPE CASUAL SHOES , Women's Dansko Professional "Sonja" Black patent Leather Mules clogs 36 (6 US)New! Womens Skechers 11910 Agility Saving Grace Athletic Shoes Grey/Aqua I14 , Men’s Ralph Lauren Brown Suede Slipper Shoes Sz Medium NWOBNew DC Shoes Girls Kids Court Graffik Sneaker Trainer Skate Casual White Sz 6New Women Authentic American Heritage SO Flash Sneakers Shoes Size 9.5 - BlushNew Easy Spirit "Medley" Women's Size (7.5 M) Walking Comfort Shoes- WhiteNew Balance Women's Vazee Verge V1 Track Shoe , Nike Free RN 2017 Womens 880840-404 Binary Sky Blue Knit Running Shoes Size 7SAUCONY KINETA RELAY LR ATHLETIC SHOES PICK SIZE NW , Air Max Dynasty Womens Size 7.5 Running Shoes White Pink Grey 816748 102 DefectDolce Vita Size 7.5 Zaren Black Leather Fashion Sneakers New Womens ShoesSkechers Womens EZ Flex 3.0 TAKE A Chance Wide , Vans Sk8-Hi Slim ( Foil Metallic) Silver/White- Women's Size 5.5Hi-Tec Harmony Life 24002 Waterproof Hiking Trail Shoes Tan Gray Womens 9.5 NIBBrooks Revel Navy/Light Blue Running Shoes Women's US Size 9.5 (E1,11) , Womens sz 6.5 B M Brooks Chariot Bittersweet Red Orange Heritage Running ShoesCute?? Nike Free 5.0 2014 Hyper Punch Jade Bright Mango Sz 8 642199-600 YogaVans Womens Classic Slip On LX Polka Dots Black White BRAND NEW!Salomon Crossamphibian Swift Women's Fig/White/Sangria Water Shoe 9.5M
"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."