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.Mens Lands End Driving Mocs Size 11.5MFlannel Women's Flats Black Size 37 , Sam Edelman Felicia Women Ballet Flats Leather Soft Elastic Metallic Gold 6.5 MGROSBY ELLE BLACK CLOSED TOE WOMENS FLAT WORK CASUAL SHOES STRAP WEDGES FLATS , LAUREN Ralph Lauren Belen Leather Loafers, Women's Size 6.5 B, Black (Damage)BC womens Brown Leather Mary Janes Size 9 M , Women Lady's Shoes Flat Shoes Casual Shoes Athletic Sports Running Shoes Trainer , Eastland Size 8.5 Women Shoes Syracuse Casual Slip On Brown Buckle LeatherLands End Everyday MaryJane Shoes for Women Black/Blue SZ 7/7.5/8 NEW $49.5Sanita Clogs Womens Size 38 Shoes Burgundy Gold Floral Tapestry FabricNEW STAR Women Outdoor Sneakers Fashion Comfortable Black Shoes 4556 e_N , Italian Pink Pearlized Leather Open Shank Dress Shoes Size 36-39 /US Womens 6-9Womens Vouge Leather Gold Leaf Flats Heel Slipper Summer Shoes Sandals FlipflopsLanvin Pewter Leather Peep Toe Ballet Flats Size 6 , Aldo Womens telassi Closed Toe Mules, Black, Size 8.0 IvoE , New Men Flip Flop Beach Holiday Sport Sandal Vogue Slip On Slipper Rubber ShoesLevi's Women's Stan G Black Denim Sneakers Comfort Tech Black/White Size 7.5 A63Skechers 15200 BBK Women's Go Run Ride 7 Running Shoe Black Size 8.5 USClarks Womens Shoes Wave Trek Sneakers Waterproof Walking Leather Size 7MFila Womens Xtenuate Running Shoe- Pick SZ/Color.PUMA Women's Basket Classic Metal Sneaker , Women's CHUCK TAYLOR ALL STAR HIGH TOP Silver Gray Sparkle Glitter Sneakers 10 MEUC! Converse All Star Chuck Taylor Sneakers Hello Kitty pink canvas m 7.5 w 9.5Nike Free RN Women's Running Shoe 831509 601 Size 6 , Paperplanes Womens Air Cap Running Shoes Trainers Athletic Sneakers GR 1408 CA , NIKE WOMEN'S ROSHE ONE FLYKNIT SHOES SIZE 11 laser orange mango sail 704927 802Adidas Kids 6.5 EQT Support ADV J Shoes Women's Size 8.5 Pink/White NEWWomen's Asics Gel Dedicate 4 Preowned Tennis Shoe Size 8.5Women's Karhu Forward Fulcrum New Royal/Spirit D200105 Brand New WITHOUT Box , Brooks Ravenna 6 Womens Running Training Shoes Size 6.5 Blue Pink Green ,
"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."