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.G. H. Bass Sheena Black Floral Tooled Mules Clogs Shoes Womens Size 6.5 M , Kelly & Katie Womens Cigola Pointed Toe Loafers Light Pink Size 8.5 b2w9 , Footsmart Slip On 9.5 Red Leather Comfort Dress Shoes Flats Gathered ToesLuichiny Womens Vay Kay Brown Casual Shoes Sneakers 6.5 Medium (B,M) BHFO 2586 , Vintage Mister Shoes Black Flats 6.5BWomen's SANUK FUNKY FIONA Slip On - Size US 7 , BOC Born Concept Brown Leather Buckle Mules Slip On Clogs Womans Size 8Aerosoles Luv Fest Suede Loafers – Size 7 – NEW W/O BOXKalso EARTH ANARCHY BLACK ZIP FRONT WALKING SHOES Sz, 5.5Women's Vince Camuto Evy Black Slip On Ballet Flats Leather Shoes Size 6 M NEW!Sam Edelman Women's Becker Fashion Sneaker, Pastel/Black, 8.5 M USRyka Orleans Navy Blue Leather & Plaid Slip-on Boat Shoes NEW , NEW Adrienne Vittadini SHOES COW PRINT Brown & Cream Calf Fur Flats LOAFERS 7Womens Low Heel Flat Chunky Studded Sandals Summer Black Biker Buckles Goth SizeSkechers Street Women's Moda-Clean Street Fashion Sneaker,White/Pink,7.5 M US , SAS Handsewn Shoes Womens 4.5 M Black Leather Penny Loafers Slip On Comfort USALucky Brand Womens cardyn Closed Toe Mules, Black, Size 9.0 xcVzNew Balance Womens W690v4 Blue/Pink Running Shoes Size 12 (333905) , ADIDAS Women's White Pink Running Tennis Sneakers Shoes SIZE 7.5 !Asics GEL-SCRAM Women's Shoe Athletic Pink Blue T2J6N Running Sneaker sz 9.5 , Adidas Ladies Chen Tao Shoes - New - Sz 8 - White w/ Magenta Stripes , Womens sz 8.5 M Rockport truWALKzero Rock On Moreza pink sneaker shoes washableNike Women's Roshe One Winter Running SneakerWomen Nike In Season Training 6 And Running Shoes Gray volt 852449 002 Size 6.5 , Ahnu Womens Yoga Flex Cross Trainer Sneaker Shoes Snow Melt US 8Mizuno Women's Wave Catalyst Running Shoe, Atomic Blue/White, 7.5 B US , Ricardo B.H. Women's P32 BootieNike Zoom Soldier VII Lebron James 610343-600 Basketball Shoes Women's 7.5 , Womens Hi-Tec Penrith Low Walking Waterproof Hiking Outdoors TrainersMerrell Womens Moab Ventilator Breathable Hiking Athletic Shoes Size 6
"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."