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.Airwalk Women's Slip On Canvas Sneaker Size 10 Floral , Lucky Brands Flats Size 8 1/2 Suede BrownSAS Tripad Comfort Metallic Bronze Slip On Loafers Shoes Women's Size: 8.5 M , VINTAGE HUSH PUPPIES Olive Green Suede Leather Slip On Loafers - Women's 8Tahari Jules Ballet Flats Snakeskin Print Brown Patent Leather Buckle Shoes 7.5 , Paul Mayer Attitudes, Snake Leather with Black Cap Toe Ballet Flats size 6.5 B , NIB J Crew Baja Suede Flat Espadrilles Size 8Cobb Hill Women's Wow-CH Flat, Pewter, 7 MRieker Womens Daisy 15 Slip-on Size 9new $175 THERESIA M. Graham tan driving shoes FLATS Made in Germany US 5.5EUC Dansko Brown Leather Mary Jane Platform Shoes Clogs Sz 38A35 Oceanaa Classic Loafers 015, Black, 9 USSoftWalk Women's Naperville Ballet Flat, Black/Black, Size 7.0 POyVNew Kenneth Cole White Jovie 2 Leather Sneakers Shoes Sizes 7 or 10Skechers Adventure - Tan with light green - Size 6.5Naughty Monkey Womens andromeda Fabric Low Top Slip On Fashion SneakersARRAY Womens Closed Toe Loafers Pewter Size 12.0 V0zwSperry Seacoast Casual Shoes - Girls' Size 4.5 M, Navy , GUC Women's New Balance Gray Fresh Foam Running Shoes Sz 8 B , 02-806 Asics Comutora Black White Women Gear Running Sneakers T881N SZ 8.5NIKE WOMENS AIR RIFT SZ 5 ARTISAN TEAL LT RETRO 315766 301Brooks Glycerin 13 Running Sneakers Gray 11 M Women , New Balance Womens White/Pink Cross Training Shoes Size 11 (16820) , Adidas Originals Trainers Leopard Suede Print Sneaker Shoe Womens 11 Casual , Women's Skechers Relaxed Fit VALERIS Training Shoes Sneakers Gray /Mint Size 8.5STEVE MADDEN BERTIE Women sneakers (9.5M, WHITE)UNDER ARMOUR UA Assert II Running Shoes Womens Size 9.5 Black Green 1233615-002 , New! Women's Skechers Knit Glider 2.0 Slip On Shoe Black 22882 4Y , Newton Running Kismet II Pink, Green Women's US Size 10.5 (D2,4) , VIONIC 335TOURNEY9004 Action Tourney Women's Walking Sneakers Blue Teal Size 8M ,
"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."