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 Taupe Brown Suede Clogs Mules Slip On D29428 Size 9.5 B , Airwalk Womens Brown Camo Casual Slip-on Sneaker Loafer Shoe - Size 9.5MMERRELL KULA SLIDE Slip On Mules Performance Shoes Women's Sz 6.5 Aqua Blue Mesh , Skechers Mary Jane Shoes Sz 8 Brown Distressed Leather Suede Flats Loafer 21571Women Canvas Loafers Spring Casual Slip On Shoes Floral Summer Walking Shoes , Brand New Sperry Pier Side Perforated Leather Slip On Sneakers White Size 6 , **Steven By Steve Madden Kenner Casual Slip On Shoes - Women's Size 6.5 - Black , Clarks Bendables Womens Black Leather Slip On Shoes Size 6M Loafers , Trotters Simmy Leather Mary Janes, Women's Size 10.5 W, Bisque , Snakeskin Black Burberry shoes Heels women size 38 , Nike Delight V Women's White Black Leather Golf Shoes 651997-100 - US 7 () , Anne Klein Women's Bette Two-Piece Pointed Toe Flat , VINTAGE NIKE WOMEN'S AIR MAX FLASH ORANGE GRAY SIZE 8.5 , VANS OFF THE WALL MENS BLUE SIZE 10 VERY NICE , Black Men's Sandals Sport Slides Beach Slippers House Shoes Slip On Footwear New , ~ CUSTOM SARAH JESSICA PARKER BITTEN WOMEN'S convese like ATHLETIC SHOES SIZE 8 , New balance 421 Women’s Running Shoes Size 8Nike Flex TR 7 Training Shoes - Women's Size 8 - Gray , Nike Wmns Air Max Zero PRM / SI / QS Womens Running Shoes NSW Sneakers Pick 1 , Summit White Mountain Women's Andrea Mary Jane PumpConverse All Star Collar Studs - Baskets montantes en toile , Womens Brooks Mazama Athletic Support Mesh Cross-Training Running Shoes Size 7.5Converse Revival Ox Womens Retro Shoe All Black Sz , Roxy Bayshore III Shoe - Tan - New , Women's Vans Authentic Pop Dots White Aqua Sea VN0A348ALS2 Brand NewWomen's Vibram Fivefingers Pink Sport Shoes Size 8.5 M , Asics GT-2000 4 Women's Silver/Turquoise/Lime Punch Running Shoe 9M , Reebok Women's Stylescape 2.0 Arch Fashion Sneaker - Choose SZ/Color , Saucony Women’s Pinnacle 2 Running Shoe - Size 9 White/Silver/Blue.Saucony Women's SHADOW 5000 MAIN SQUEEZE Running Shoes Lime S60033-75 a1 ,
"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."