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.Vans Women’s Size 11 Boat Shoes Slip On Black White Stripe Espadrilles , Sanita Womens Shoes Sandals Clogs Open Toe Open Back Danish Size 37 Red LeatherNine West Women's Luvintrist Fabric Ballet Flat, Black-Pink/Black, 9.5 M USBirkenstock size 37 (L-6) tan suede slide on Clogs / Shoes , Easy street, dark silver Low wedge slingback Sandals M. , Elizabeth Casual Comfort Flat Shoe -Sand 8.5MBorn BOC Black Leather Mary Jane Flats Shoes Womens Size 9.5 M c93403 soft , Tod’s Black Velvet Leather Loafer Moccasins Driving Shoe Womens Size 5 , Klogs Natalie Women's Clogs Display Model Shoes Yankee Orleans Navy 9.5 M , New Without Box Tory Burch Sandals Flip Flops Multicolor Size 7 , Eric Michael Womens Shoes NEW $145 Omar Black Taupe Suede Slip On Platform 37 7 , *FAB* Wine Patent Leather AGL ATTILIO GIUSTI LEOMBRUNI "PARKER" Oxfords 39.5 , NEW WOMENS LADIES GROSBY - DANICA SHOES SLIPPERS SHOE NIGHT COMFORTABLE WARMCalvin Klein Womens Inca 2 White Fashion Sneakers Shoes 7 Medium (B,M) BHFO 2965Converse All Star Womens Dark Beige Canvas Shoes - Size 6STEVEN Steve Madden Women's White/Gold Peck Espadrille Platform Sneakers - NEWWomen's Sperry Top-Sider Angelfish Gold Python Boat Shoes #SP2 , Women's White Walking Sneakers Tennis Shoes Etienne Aigner- Steffi Size 10 M NEWZara Fashion Sneakers Shoes Sz 7 Womens NewSkechers Shape-Ups White/Purple Walking Shoes Womens SN 12320 Size 9.5 (B1)Women Casual Flat Platform Sneakers Ladies School Creeper Trainers Sport ShoesWomen's New Balance Sz 11 M WX20BW2 Mesh Black Sneakers Lightweight Vegan , Unisex Breathable Athletic Sport Shoes Cross Trainers Fashion Sneakers for Gym , Avia Women's GFC Studio II Cross TrainerASICS Womens Blue Walking Shoes Size 6 (356563) , Altra Womens Provision 3.0 Purple Athletic Trail Road Running Shoes Size 9.5 , GEOX Leather Block Heel Ankle Boots - Annya Mid BLACK 6m , Adidas Originals Womens Stan Smith Sneakers White Green Size 6.5ASICS Gel Galaxy 5 White Black Berry Womens Running Shoes Sneakers Size 11 T281NNEW Balance 608v4 Women's White And Pink Size 9.5 9 1/2
"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."