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.Minnetonka Thunderbird Beaded White Leather Moccasins Shoes 7Brighton Dawn Classic Brown Leather Croc Print Loafers Shoes sz 6.5M ItalyChristopher Natalia Diamond Ladies Silver Flower Wedding Womens Heel Shoes Satin , Christian Siriano For Payless Black Slingbacks Flats Womens Shoes Size 6.5/37 , New Women Summer Retro Glitter Buckle Slingback Jelly Rubber Sandals Heel Shoes , Spot On Ladies Floral Print PimsollsKEDS SPORT Women’s navy Blue Moccasin Loafer Boat Shoes Size 9.5Tory Burch Gold Logo Flat Sandals Shoes Ankle Strap Size 9.5Womens Comfort Loafers BLACK & WHITE Fur & Leather Zebra 8.5 M Brazil , Besides! Wonderfully Light-weight Slip-on Espadrille Boat Shoe Flats Red Linen , Ralph Lauren Leather Heeled LoafersXielong Womens Chaste Ballet Flat Red Lambskin Loafers Size 7Rockport Cobb Hill Collection Women's Paulette Slip-On Red Size 6 WideDolche Vita Womens Women's Zalen Fashion Sneakers ~ Size 41,5/US 10 , ADIDAS WOMEN'S CF LITE RACER ATHLETIC COMFORT SHOES,AC8475,BLACK/WHITE,MEDIUMSoft Spot Supremes Courage Women's Size 6 EE , Vionic Women's Action Sunset Mary Janes Dark Grey Style 334Dr. Scholl's Anna Canvas Sneakers, Women's - Size 8 M, Navy , Womens Skechers EZ Flex 2 Gray Chasing Dreams Slip On Memory Foam Shoes 5 , Womens Nike Air Max Zero Provence Purple Size 7 , Skechers Size 6.5 Womens Black Kiss HAPPY MOMENT Stretch Fit Comfort Nurses Shoe , Rocket Dog MISTIESD Womens Mistie Sneaker- Choose SZ/Color.Women's KS35 Jazmin Loafer Flats, Black Durability Flats , Nike Women's Flex Contact Running Shoes Bordeaux/Tea Berry/Pink Nebula 5 , EUC! Converse All Star Chuck Taylor Sneakers Hello Kitty pink canvas m 7.5 w 9.5Adidas RESPONSE LT Women Running Shoes Adidas Boost Sneakers BA7784 BR# , Propet TravelFit - Purple - WomensCOLUMBIA TECHLITE 800 TRAIL SHOES Women's Size 7.5 WMNS BL3662-010 Mint Cond , Skechers Dynamight Blissful Navy White Womens Trainers Shoes , New Balance Womens WLD5KV4 Track Shoes- Pick SZ/Color. ,
"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."