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 MERREL Black Suede Casual Mary Janes Flats Driving Shoe w Buckle 7M - LNCWomen Leopard Suede Pointy Toe Loafer Flat Slip On Casual Comfy Flats Shoes , Sperry Women's LIGHT GREY TOPSIDER LASERCUT 8.5M EUC P24 , WOW! COLE HAAN COUNTY BROWN 7.5B SLIDES HEEL, WITH BOX GENLY USED EUC! , Women's Dr Scholl's Really Flats BlackSperry Top-Sider Unisex CVO Blue Canvas Sneaker Boat ShoesPrivo Clarks Black White Flower Toe Canvas Slip On Flats Women’s Shoes Size 6.5Soft Science Size 11 The Fin Blue Light Walking Boat Oxford ShoeDr. WEIL orthaheel Taupe Nubuck Leather DEVA Clogs 7 38 Flower Detail , ZARA GENUINE SHINY PLIMSOL BLOGGERS FAVE BNWT BLACK 9 USSoft Spots Angie Taupe Leather Loafers Shoes , Pleaser 2" PF Creeper W/ Metal Zipper Adult Women Flats Blk Leather Shoes , ME TOO YALE FLATS BLKNUB WOMEN'S SIZE 9.5 , SPERRY TOP SIDER "COASTLINE" MARY JANE SHOES LADIES US 7 MED NEW , LADIES SHOES/FOOTWEAR -Cherry Sweeter navy moccasinsaucony ride 9 womens size 8.5 washed air dried run walkNIB MINNETONKA Size 8 Mens Tan 100% Suede Sheepskin/Shearling Soft Sole Slippers , Lot of 3 Pairs of Baby Phat Ladies Sizes 7, 7.5 & 8.5 , Rares baskets BRONX 40, 41, portées 1 fois !New Balance 696 WL696KP N Brown Retro Polka Dot Running Shoes Women's 7 B EUC , UNISEX REEBOK OSR HARMONY RACER BD4638 BLL/BLUE//WHITE/YELLOW DS BRAND NEWKEEN TARGHEE ll DARK EARTH / ALLURE HIKING TRAIL SHOES BACKPACKING EUC FREE SHIPWomen's WOMEN REEBOK WHITE PRINCESS 1475 Carmel, Delicate Athletic ShoesReebok One Trainer 2.0 GR Running Training Pink & Teal Sneakers Shoes Womens 9.5 , Puma Woman Knockout Bright Pink High Top Gym Shoes Sneakers w Soft Foam insole , Brooks Glycerin 15 Size US 7.5 M (B) Aqua Blue Women's Running Shoes 1202471B476Saucony Womens Zealot Iso 2 running Shoe- Pick SZ/Color. , Adidas SL Loop Racer Womens Size 6 Blue/Purple/Black/White - Great Condition , Puma Phenom White - Womens - Size 8.5 BWomen’s ASICS Gel Kayano 21 Running Shoes Sz 10 T4H7Q Mint green Black $165 ,
"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."