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.Born Slides Mules Brown leather Size 10 42 Slip On Casual 3" Heel ShoesCabin Creek BLACK SHOES WOMENS SIZE 7 MPW MINOR brown leather SOFIA Mary Jane comfort cushion insole walking shoes 7Blue Leather Antonio Melani 9M Driving Slides Loafers Slip on Flats , Covington Slip On Closed Toe Shoes LAURAN 8MCorkys Sidewalk - Bronze - Womens 9Women Loafers Leather Oxford Slip On Walking Flats Anti-Skid Boat Shoes 7 B M... , Ecco Wmns Sz 41 US 10 Loafers Brown Leather Heels Comfort Career ShoesLucky Brand Emmie Round Toe Ballet Flats 976, Brindle, 6 US / 36 EU , Nice **SPERRY TOP SIDER** 2 Eye Turquoise Faux Patent Leather Deck Shoe, 7 M , ETIENNE AIGNER WOMEN'S 6 1/2M 6.5 M BLACk LEATHER CASUAL FLAT LOAFERS SHOES , NWT CROCS CAP TOE Tortoise FLAT Women 11 BROWN Authentic Working DRESS Shoes , SPERRY TOP SIDER AVERY LEATHER KILTIE PENNY LOAFERS BOAT SHOES WOMEN'S SIZE 8.5 , Sperry "Crest Vibe" Sneakers Navy 10 M With Memory FoamSoludos Women's Wren Platform Smoking SlipperAuth Fendi Black Patent Leather ballet flats Size 40I35 Galle Studded Loafer Flats 607, Black Lips, 9.5 USRYKA Synergy Womens Size 8.5 Black/Lime Ortholite Comfort Running/Walking Shoes , Graffiti Women Ladies Running Shoes Mesh Breathable Sneakers Ultralight Shoes , Skechers Gold Metallic MEsh Mary Jane Fashion Slip on Athletic Shoes 7.Earth Brown Leather Mary Jane Womens Shoes Kalso Technology Size 9B , adidas Womens adiZero Ambition, Tribe Purple/White/Orange, 7 B USWomen's Mephisto Comfort gray Leather Oxford Shoes size 6Women's Sanuk Fiona Burgundy Chevron Shoes Elegant Shape Flats , Women's "Torrid" Flats~Black~Horsebuckle~9W~NWOB Elegant Appearance FlatsZumba Street Groove Shoes - Coral , Minnetonka Women's Grace Moccasin Gold Leather Moccasins , NEW KEDS Canvas BLACK Shoes Champion Ox Canvas Size:6.5 6 1/2 WF2774 NIB Box , Adidas Shoes Stella McCartney Irana AQ1996 Blue/ Yellow Women's Size 1023259 Black Skechers shoe Memory Foam Women Comfort Casual Slipon Sporty Sneaker
"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."