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.NICOLE MILLER NEW YORK WOMEN'S DAHLIA FLATS BLACK/BEIGE CANVAS US SIZE 9 MEDIUMTROTTERS "Taylor" Burgundy Leather Flat Slip On Loafers - Size 8.5W EUC! , Croft & Barrow Ortholite Womens Navy Blue Casual Cut Out Slip-On Shoes - Size 9 , New Arrival Women Flats Shoes Women Loafers Ladies Slip On Flats Women Shoes , Women's Highlights Black Loafers, Size 7 1/2 WSIMPLE Womens Casual Oxfords Shoes Blue Size 8.5 / 39.5 Walking , Sperry Topsiders Shore Path Womens 8.5M 2 Eye Boat Shoes Navy Canvas Y481Robert Zur Gunmetal True Glove leather Braided Grey loafers 6.5AA , DANSKIN NOW LADIES/WOMEN ATHLETIC SHOES/MULES SIZE 11 , Skechers Go Walk Womens US 9.5 Gray Suede Style Walking Shoe - 1097 , NEW adidas outdoor Women's Shoes Terrex Voyager CW CP W . Pick your size , Nike Free 5.0 Running Shoes, Lavender/Grey, Womens US Size 7New BZEES Blue WISH Mary Jane Water Shoe 6 $69 Sea Dogs NIB , NEW Skechers Flex Appeal 2.0 AirCooled Memory Foam Womens Sneakers Size 8.5Men's Shoes Slippers Old Friend Men's Slipper Exquisite (in) Workmanship SlippersWomen's Birki's Orange Shoe--Size 8--Eur 39 Wholesale Flats , SKECHERS 12418 Skechers Womens Empire Sharp Thinking Slip-On- Choose SZ/Color. , Shoes Puma Cross Shot L Women's 357150 01 Sneakers Basket Moda WhiteReebok Women's Hexaffect 5.0 MTM Running Shoe, Mist/White/Black, 7 M US , New Women Vans Authentic Black Skateboarding Shoes Classic Canvas size US 6Tommy Hilfiger Womens Two Sneaker- Pick SZ/Color.Skechers Women's Double up-Duvet Sneaker - Choose SZ/ColorAerosoles Women's Midpoint Ankle Cuff Sandal Taupe Faux Leather Hook and Loop , PUMA Suede Heart Quilted Cordovan/Marshmallow/Metallic Cameo Brown 36546201Vans Emory Navy Skateboarding Shoes 5217375 Youth's 4.5,5,6 Women's 6,6.5,7.5NWT WOMENS UNDER ARMOUR W CHARGED BANDIT 2 TRAINING RUNNING SHOES SZ 6-8 , Fila Womens Forward 3 Running Shoe- Pick SZ/Color.La Sportiva Womens Akasha Gray Athletic Trail Running Shoes Size US 7Paul Green Women's Patent Leather Oxford Shoes Sz 7 US 4.5 UK Black , Vibram Women's KSO Running Shoe 37 M EU, Black/Black ,
"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."