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.SCASINI Black Fabric Slip On Shoes 1" Heels Pointed ToesWomens Size 6M Adorable!Women Men Fashion Casual Health Canvas Flat Shoes Jean Guy Snowy Size 35 , Bass Women's Shoes Size 9M Black JoJo Velcro Stretch Comfy Slip-onsWomens Flats Pointed Toe Faux Leather Ballet Casual Slip On Lady Shoes New size , London Underground new women shoes black tie leather size 8.5Rag and Bone Patent Leather Round Cap Toe Ballet Flats shoes Italy Sz39.5 suedeEMPORIO ARMANI BLACK SUEDE SANDALS 39DC Shoes Women's Rebound Hi Top Skater Shoes US Sz 8.5 EU Sz 40 blue green E18 , Merrell Womens Performance Shoes Size 7.5 Wild Dove Eggshell Blue , Skechers Shape Ups White Size 8 Womens A8BRASH Sneakers Women Shoes Size 7.5 Black / White / Silver (New)Women’s Nike Zoom Hyperquickness TB Basketball Shoes 599515-001 Size 7 Black , New Balance 1140 Running Shoes, #W1140B1, Grey/Blue/Pink, Womens US Sz 8NICE Women's New Balance SD400 Track & Field, Cross Country Spike Shoes - Sz 10 , NIB Women's Ecko Sneakers Athletic Shoes sz 7BROOKS "ADDICTION WALKER" women's 6N white leather linear platform walking shoes , Women's SKECHERS GO STEP LITE PERSISTENCE Blue Slip On Athletic Shoe 14710Fred Perry Aubyn Velour Womens Red Mahogany Textile TrainersDr. Scholl's Womens Flyer Black Microfiber Running Shoes Size 8.5 (25067)Women's Skechers Skech Knit Flex Appeal Cosmic Rays Multi-Color Sneakers Sz 9.5PUMA Suede Classic Sneaker Gray Pink Size 6.5 NIB $65 , Skechers Shape Ups 2.0 Comfort Stride Model 57003 Women’s Size 10 Black WhiteSalomon Womens trail shoes size 9Nike WOMEN'S Air Max Thea KJCRD Black/Bright Crimson SIZE 6.5 NEWASICS Women's GEL-Sayuri Athletic Running Shoes - Black , New women's Sneakers Chic Shoes Sequins Hidden Heel Wedge Sports High Top SizeNike Air Force High Top white Size 6.5 Women Hi Top Vintage made korea bowermanMW009530 - FASHION STRETCH FABRIC HIGH TOP SNEAKERS (SIZE 35 - 43) , Puma Womens Size 9.5 Basket Classic Gold Black Metal Sneakers ShoesPuma match basic Puma white ultra magenta Free shipping
"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."