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.Clarks Artisan Womens Kadri Leah Womens Loafers Slip On Leather Shoes Sz 8NATURALIZER NATALIA Front Zip Slip On Leather Loafers Black Womens Size 11M ZQBELINDA Slip On Casual Party Ballet Flats Office Oxford Women Shoes Silver 9.... , Women's Dockers leather slide on shoes flat brown US size 6 , IKRUSH Womens Sienna Bow Platform Pump Trainer , Sperry Top-Sider Womens SZ 7.5M Gray Plaid Boat Shoes SC8SH5 Allen Edmonds Women 8.5AA USA Linden Chukka Bootie Brown Leather Shoe OxfordMUNRO American Women's Suede Patent Bicycle Toe Walking Sneaker Oxford 8M USAChic Women Chunky Heels Sandals Pointy Toe Slip on Mesh Rhinestones Casual ShoesWomens Sperry Top Sider Angelfish Boat Shoes Size US 10 M Purple White Plaid , Tahari Paulina Slingback Tassel Pointed Toe Loafers, Preppy Navy, 5.5 US , Calceo Clog Leather Slip On Mule/Clog Elephant Burgundy New Size 8 Women Shoes , **Clarks Cloudsteppers- Sillian Jetay Flat, Women's Size 7 W, KhakiADIDAS Women or Youth Black with Vibrant Orange HIGH TOP SHOES sz 6.5 M , Nike Woman's Dunk High Skibny shoes size 6 , New Women Sneakers Athletic Shoes Running Walking Training Sport Casual ComfyLaser Peep toe Creepers Shoes Womens Casual Pointy toe Wedge Heel Pumps ShoppingWomens Skechers Shape-Ups Fitness Shoes Size 9 White Style 11800Merrell Black Nylon Leather Casual Hiking Trail Clog Slide Shoes Women's Size 6 , Women's Ladies Wedges Sneakers Sequins Shake Shoes Fashion Girls Sport Shoes , ASICS CUMULUS 18 RUNNING SHOES / MULTI COLOR ( SIZE 8.5 ) WOMEN’S , Women's Privio women 12M Trendy FlatsShoes Puma Vikky Platform 363287 01 sneakers woman Black Memory Foam Retrò Litd , White Mountain Women's Lewis Slip-On Shoe Black Metallic , Skechers Women's Go Walk Lite-Smitten Loafer Flat - Choose SZ/Coloradidas Terrex Womens Voyager Black Hiking Shoes, 7.5NEW! LACOSTE TRINITY PUNCHED WOMENS WHITE LEATHER SNEAKER TENNIS SHOE US SZ 5.5 , Nike Women's Roshe Two Flyknit Athletic Shoes US Women Size 7 , New Balance Womens 77v1 Vazee Transform Training Shoe, Porcelain/Blue, 7 B USSkechers Bikers Springform Leather Walking/Hiking/Biking Shoes Women's Size 10 ,
"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."