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.NEW! Avon Women's Studded Loafer Black 426PQRST dzNew Womens Oxfords Flats Slip on Breathable Leather Casual Sneakers Shoes 2018DR. MARTENS WOMEN'S YVONNE SLIP-ON SHOES BLACK LEATHER 8 MEDIUM 6 UK $110 , rosalba-01y New Flats Casual Comfortable Simple Cute Office Women Shoes musf 6.5Women's Steve Madden Gatsby Size 7.5M Clogs Booties Shoes Red Leather Wedge U4Sugar Skulls Fashion Lightweight Slip-on Canvas Women's Casual Flats ShoesAEROSOLES METALLIC LIGHT PURPLE LAVENDER LEATHER COMFORT BALLET FLATS SIZE 9White Mountain Prue Slip On Loafers, Black, 10 US , Nautica Women's Ladar Fashion Sneaker US 6.5 , Klogs Naples Clogs - Women's Size 8 M, BlackJosef Seibel US 11 to 11.5 Black Oxford Women'sCamper Size 40 US 9 Ivory Off-White Leather Mary Janes Ballet Flats , Robert Zur Women's 'Petra' In White Glove Leather 7 M $245 New , Girls Womens Round Toe Sequins Mesh Hidden Heels Breathable Casual Sneakers G , CONVERSE CHUCK TAYLOR ALL STAR Chucks High Top Sneakers Two Layer 5.5 Brown TanPuma Womens Corduroy And Fur Sneakers Slip Ons Size 9 , Nike Shox 324749-111 Turbo VII White & Silver Running Shoes Women's Size 6.5Dr. Scholl's Windswept Slip On Sneakers, Women's Size 10M, BlackNike Tanjun Running Women's Shoes Size 7NEW Women's Shoes Sperry Top Sider DUCKLING Waterproof Navy Rain Boots-Size 7 , Brand New Womens Blue Under Armour Micro Speed Swift 2 Tennis Shoes, 7 , New Balance Womens WC696WT3 Tennis Size SZ 8.5 B , NIKE Zoom Equalon 3 Bowerman Series Women's Sneakers Size 9 Running Shoes 333607Women's SKECHERS GO WALK JOY 15649/BBK , Adidas Neo Courtset Sneakers In Light Pink Women's Size 10 , NEW WOMENS AEROSPORT STRIDE ATHLETIC SPORTS SPORT GYM YOGA RUNNERS SHOESNew Balance Women's 623 SG Suregrip Work Grey Suede Sneakers Size 6Naturalizer Women's Junction Fashion Sneaker, Silver, 8.5 M USWalking Cradles Women's Ace Slip OnWomen's 8 CONVERSE ALL STAR Chuck Taylor Black Canvas Sneakers New
"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."