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.Women's Black Suede Leather Pumps ZEITGEIST Sz 8, Cute, Made in Italy , Rust Brown Suede Moccasins Size 6.5M By NATURALIZER Made in the USASimply Vera Vera Wang Women's Moss Grey Beaded Pointed-Toe Flats - Asst SizesJOLIE PAIRE DE BALLERINES TOUT CUIR 38 , WOMEN'S CLARKS UN-STRUCTURED BLACK LEATHER LOAFERS, SIZE 8.5 MTahari Women's Vivian Ballet Flats Floral/Leaf/Paisley Magenta Leather Size 6 M , Brand New Dr Comfort Women's Sunshine Mary Jane Leather Diabetic Shoes MSRP $174US DRESS SHOES FOR WOMEN ETHNIC DESIGNER SHOES WIDE SHOES PUNJABI JUTTIES DD860 , Aetrex Women's Bungee Oxford Blackberry Size 7.5 zwGQEasy Street Women's Kacey Flat, Brown Flannel/Snake, 6.5 W US , Nike Air Max Torch 4 Running Shoes 343851-036 Women's sz 8 , Kamik Dublin Shoes Waterproof Faux-Shearling Women Size 8 EUC Slip OnsNEW Womens Arcopedico Black Mesh Flat Walking Shoes Size / US 9.5-10Perry Ellis Portfolio Mens Microsuede Slippers Black or Brown Asst Sizes NIBSaucony Outduel Shoes Women's Size 6BOBS from Skechers 32502 Womens Bobs Squad-Total Glam- Choose SZ/Color. , Nike Kawa Slide Womens Style : 834588 BLACK/VIVID PINK Womens Size 12 , ADIDAS Women's PURE-BOOST Q4 Running Shoes/Sneakers BNIBKeds Women's Craze Sneaker, Black, 9.5 M US , Waldlaufer Hiroko-Soft Black Anthracite Womens Leather Nubuck Shoes TrainersMizuno Paradox 2 Running Shoes Size 7.5 FREE SHIPPINGASICS RoadHawk FF Sneaker, Women's Size 7, Dark Grey/Silver/Glacier Sea , New Womens Black, Gray & Red Adidas Galaxy Trail Tennis Shoes, Size 7.5Women's Nike Roshe Two Flyknit 365 Shoes NEW Blue/Grey/White/Fog, MSRP $140Nike Roshe Two Flyknit V2 Women's Running Shoe Navy White us 6.5woman tennis shoes DC Comic girl low top supergirl new with box navy pink starsVANS New Authentic Lite Canvas Vault Lady size USA 7 , ASICS Womens - Blue Running Shoes Size 10 (366309)Propét Womens Dagny Low Top Zipper Fashion Sneakers, Black, Size 8.5 , Anne Klein Womens Zasa Low Top Slip On Fashion Sneakers White Multi Size 5.5 J
"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."