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.Sperry Top Sider Sail Beach Navy Canvas 2-eye Boat Shoes Women's 11M - usedSteve Madden P-Heaven Black Flat Women's Shoes Size 7.5 AL4373 , Grasshoppers Ortholite Wedge Shoes Slip On 10M Red Striped Round Toe MISTYREGENT-11! Qupid Women's Bow Velvet Slip On Loafers Flats , Sperry Top-Sider Pier View Elastic Gray Canvas Boat Shoes Women's Size 7 M , Womens Twisted X Driving Mocs D Toe USA size 10 M Bomber , Tory Burch Reva Flats 5 M Black Patent Ballet Shoes , Poetic Licence Danty Doll Checkerboard Gray Black Rhinestone Bow Size 6M NEWPrivo by Clarks Womens leather slip on shoes 9 M , Sanuk Shorty Ice Chill Dusty Peri Icicle Women's Loafer 1017598 , Sofft 8.5 W Brown Leopard Print Tassel Loafers Women's FlatsGrasshoppers womens Black Comfort Slip On Loafers Sz 8 I302 , Womens College Creepers Canvas Platform Athletic Casual Sneakers Sports Shoes , 2018 Hot New Authentic Tom Women's Classic Slip On Shoes-- , Trotters Women's Sizzle Ballet Flat, Burgundy, 10.5 W US , Asics Women’s GEL-Storm Running Shoes Black Onyx Emerald Size 10 M , ASICS GT-1000 women's running shoes 8.5 T6A8N FAST SHIPPING? , Nike Free Run TR Fit 5 - Blue/Teal Running, Cross Training (Women's 7.5) - UsedBNWT Mens Size AUS 6-7 Rivers Brand Smart Navy Blue Checked Fabric Slippers , NEW BALANCE 711 black with white trim reunning/walking sneakers SZ 7.5M , Chaco Outcross Evo Mary Jane Hiking Water Shoe Sandal Black Gray Womens Size 7 , PUMA Etoile Black Suede Athletic Sport Shoes~Lifestyle Sneakers Womens Size 8 USWomens Nike Son of Force Basketball Shoes Size 6.5 - 10 Black White 616302 006 , Nike Womens Flex Experience RN5 Running Shoes sz US 4.5 BRAND NEW , Women's Nike Air 8.5 A Great Variety Of Goods Athletic Shoes , DC 301360 Womens Villain W Skate Shoe- Choose SZ/Color.Skechers Women's Premium - Seeing Double White/Blue Casual Shoe 7 Women Us , Puma Fierce Core Womens Slip On Grey Mesh Dance Trainers 188977 03 M13Women's Nike Internationalist Desert Camo Tennis Shoes, 807407-200, Size 7New Balance running/hiking shoe -New in box. WT570. Women's Size 6.5 ,
"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."