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.HARBOR SIDES SHOES WOMENS SIZE 8 , REPORT FLAT COTTON BLUE/WHITE SHOES SIZE 6 (S278)Unsensored U-Amber Ladies Red Shoes Size 7.5 --------New In Box , BROWNS Couture Studded Leather and Wood Heel Clog Mule Shoe Size 37 , Cole Haan Clogs Platform Shoes Black Suede High Heels Slip On 7.5 BNine West Women's Lellman Ballet Flats Clear/Argent Silver Size 6 (B, M) , LAUREN RALPH LAUREN WOMEN'S BETSY STONE CRINKLE BALLET FLAT SHOE SIZE 7B , DR SCHOLL'S GARNET HILL NEW SUEDE SNEAKER NAVY NWOT Size 7Steven by Steve Madden Hilda Slip On Shoe - Women's Size 6.5 M, NavyArche Spandex brown leather pull string Shoes 9.5 M Made in FranceReebok Classic Freestyle Hi Patent Primal Red Womens Shoes CN2821 , Dr. Martens Dupree 3-eye Shoe Black UK4Teva Womens Willow Slip-On Shoe- Pick SZ/Color. , Silver Luxe Glitter Trainers / New / High QualityChampion women white/black leather/man made upper sneakers shoes size 8.5WAnne Klein Guardless Slip On Fashion Sneakers 235, Medium Orange, 8.5 US , Womens Printed Platform Sneaker Sports Athletic Hidden Heel Shoes Casual Shoes , Skechers Ladies Suede Slip On Walking Shoe Size 7.5 Brown , nike air max Aimax Running Shoes Sneakers Women Size 9.5 Great Condition , Limited ASH shoes size 39 gray metallic hi-tops gym shoe sneakers 8.5 , Saucony Kineta Relay Denim Sneakers-Women's size 10.0 BlueNike Air Zoom Pegasus 34 Women's Running Shoes ( Size 6) Grey Volt 880560-002New Kylie Jenner Puma Fierce VR Women's Size 8 Copper Training SneakerSAUCONY GRID FIYA 37 37.5 NEW omni xodus triumph ride kinvara guide mirageRyka Women's Ultimate Form Running ShoeNEW Womens New Balance turquoise WX711BH2 Athletic Running Training Shoes sz 10 , NEW adidas Women's Size 9 Originals X 17.4 FG W Black Soccer Shoes Cleats NWT , Women New Balance WX66WG Running Medium White Silver 100% Authentic Brand NewASICS Women's Gel-Fit Tempo 3 Cross-Trainer Shoe, Black/Silver/White, 7.5 M USVANS Sk8 Hi Slim (Quilted Denim) Dress Blues/Zephyr Skate Shoes WOMEN'S 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."