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.COLE HAAN NikeAir Womens US 7.5M Waterproof Brown Leather & Mesh Zip Clog ShoesROBERT ZUR ALL LEATHER W/GROMMETS SLIDE MULES FLATS SHOES WOMEN'S SIZE 6 INDIA , Thom McAn Brown Leather Shoe Boot Women’s 8Shoes Brown Canvas Slip Ons Size 7 Free Shipping , 4-a VANELI 8 M LEATHER GRAY 1" HEEL Shoes Mules ITALY , Women's Shoes MARC FISHER Black Bow Ribbon Flats 9.5SAS Tripad Comfort Oxfords Tan Leather Woman's Sz 9N FREE TIME WOMANS SHOES GUC , Zaxy Women's Luxury Ballet Flat Black Size 5.0Born Womens Born Shoes Loafers Casual Slip On Black Leather Sz 6.5 / 37 , Puma Womens Size 10 Leather/Mesh Slip-On Eco Ortholite Ballet Flat ComfortSperry Top-Sider Leather Boat Shoes sz 7 Womens Silver Metallic 9102385 , FRYE ladies 9.5m Brown leather shoes.L.L. Bean Women 11 M Trekker Gore-Tex Suede Oxford Casual Shoe BrownLucky Brand Womens Emmie Leather Closed Toe Ballet Flats Ash Grey Size 6.0***NEW*** Gola Women`s Create Trainer New Size 6 U.S.Diadora Condor S Camo High Top Sneakers Womens 5.5 Gray/Pink - NEW , SKECHERS SHAPE UPS WOMENS GYM SHOES SPORT SIZE 9 GRAY BLUE EXCELLENT , Nike Revolution 3 Women's Running Shoes Hyper Pink/ White/ Black Size 9.5(US)Women's Canvas Casual Platform Hidden Sneakers High Top Shoes Ankle Boots SzMen's Shoes Slippers MARSèLL casual slippers Quality Product Slippers , PUMA Women's Basket Platform Val FM Grey Dawn 9.5 B US , Lugz Women's Seabrook Canvas Sneaker Onyx/White/Black/Multi-Pink Canvas ShoesNike Flare Tennis Shoes Serena Williams 810964-003 Wmn's SZ 10.5 new MSRP $170Vans AUTHENTIC Checkerboard Port Royale/White Women's Shoes 7New Crocs 205103 0EA Lite Ride Black / White Women's Slip On Shoes Size 7 US , Women Genuine Leather Hidden Wedge Fashion Sneakers High Heel Trainers Boots New , VANS ISO 2 (Mesh) Black/White/White ULTRACUSH Trainer WOMEN'S Size 7.5 , NIKE WOMENS LODEN SZ 9 DARK STUCCO RIVER ROCK GUM WHITE OLIVE ROSHE 896298 006New Balance Women's 300 Shoes Blue , Adidas Performance Women's Edge Rc w Running Shoe - Choose SZ/Color ,
"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."