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.JOSEF SEIBEL LOAFER size 7 38Kelly & Katie Womens Cigola Pointed Toe Loafers Light Pink Size 8.5 Kua0Aldo Flats Pointy Toe Gray Size 10NWT! Sanuk Donna Palma Natural Black Botanical Tan Shoes SLip Ons Sz 6Minnetonka Moccasins Womens Brown Leather Loafers Size 7.5 , Earth Origins Wmns Sz 9.5M Veronica Brown Leather Wedge Slip Ons (AT11) , Calzoleria Toscana Hand Made in Italy Black Leather Ballet Flat Size 37 , New Women's Me Too Cute Taupe Tassel Slip On Ballet Flats Shoes Size 7W , NAOT Matai 36 5 Swirl Leather Mary Jane Flats Gold Black Metallic , Clarks Ortholite Comfort Shoes Slip Ons Sz 8.5 Metallic Brown Sillian Stork $85 , Cole Haan Fairmont Horsebit Leather Loafer, British Tan, Women's, 8D , Plane Women Pointed Casual Flat Low-cut Shoes golden , Nine West Womens Onlee Synthetic Pointy Toe Flat- Pick SZ/Color.2 Style Casual Womens Flowers Pumps Boat Pull On Flat Driving Shoes 4 Color New , Saucony Kilkenny Xc5 W Women's Running Shoe 19022?3 sz 7.5 M H272 , Womens Trainers Lightweight Comfort Touch Fasten Trainer ShoeFashion Women's Pointy Toe Faux Suede Flower Sequins Slip On Loafers Flats ShoesWomen's Cole Haan Bria Grand Sport Oxford Sneaker, Pink Metallic US Size 10.5 BJessica Simpson Womens Lynsey Ballet Flat- Select SZ/Color.PROPET WOMEN'S TAUPE/PUTTY PUFFIN LEATHER WALKING SHOES -NWOB- NEW SHOESConverse Womens All Star Ox Black Fashion Sneaker Size 9 (25021)Ryka Womens F5202f2 Frost Grey/White Fashion Sneaker Size 9 (31322)Dr. Scholl's Womens Kinney Greige Microfiber Fashion Sneaker Size 7.5 (28389) , Keds Women's Floral Leopard Sneakers Size 8.5 Medium; Excellent Used Condition , Women's Propet Jace Slide Sandal Attractive Design Athletic Shoes , Women's River island runners size 7UK Characteristical Athletic Shoes , Ahnu Womens W Montara II WP Hiking Shoe- Pick SZ/Color. , WOMEN'S NIKE FREE TR 6 WOLF GREY/WHITE/HYPER TURQ/GHOST GREEN- SZ 8 (833413-003)Skechers Performance Womens Go Step Walking Shoe- Pick SZ/Color. , Merrell Womens Fluorecein Waterproof Hiking Walking Shoes Plum Red Size 7 M $120 ,
"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."