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.Chinese Laundry Flats Womens Sandals 11 , Sperry Top-Sider Women 9M Blue Plaid Fabric 2-Eye Boat Deck Shoes 9561416Mule Slip On NEW Soft Leather Tan Open Toe Woman's 7.5M / 38 DONG HAI , MERRELL PLIE TAUPE WOMENS SLIP ON SPORTY MARY JANE SHOES SIZE 9.5 LEATHER J76344COLE HAAN Air Sadie Driver Wo's 6B Red Nubuck Penny Loafer D38753BOC Born Womens Clogs Sz 6/36.5 Med Black Patent Leather Casual Career ShoesNORDSTROM Black Suede Brown Alligator Slip On Flat Loafer Shoe Women Sz 10.5 S , Sanita Soft Tan Suede Clog Size 8 - 8.5 , Cole Haan Women's Flats Gilmore Ballet Rose Gold Metallic 9.5BPETER MILLAR PATENT LEATHER WOMENS LOAFERS NEW SIZE 6.5ARA Womens RACHEL Cotton/Gray Kiltie Leather Loafers Size 6 G , Nike - womens size 7.5, blue and black with periwinkle stripe , Nike Free 5 Women Orange Shoes Sz 7 , SAS Women's Size 8.5 M Black Diabetic Orthotic Walking Hook And Loop Fastening , Steve Madden Women's Lancer Fashion Sneaker, Black, Size 10.0 nmw0 , New Balance Womens Walking 577 Hook and Loop Shoes Tan Factory SecondNEW BALANCE 847V2 WALKING SHOES COMFORT WOMENS SZ 10 & 7 MISMATCHED WHITE BLUESaucony Womens S10373-3 White Blue Walking Shoes Size 9 (24428) , Mizuno size 9M Wave Inspire 9 blue womens ladies running tennis athletic shoesK-Swiss Women's Tubes Millennia CMF SneakerWomen's womens shoes Fine Quality Athletic Shoes , Womens Nike Flyknit Lunar2 Pink Trainers 620658 615 , Puma fierce women Art No 18919202 Black/gold Size 9.5. , New Women's Ryka Devotion Plus 2 Walking Shoe - navy/light blue - size 7PUMA Women's Fierce Evoknit WN's Cross-Trainer Shoe Black Whit 8 M US , Skechers Air Clear Day Girls Gray/Hot Pink 11 M Leather Athletic Sneakers New , New Balance 247 Women Revlite Grey Running Shoes New Training Gym WRL247YD , Tretorn Camden 3 Sneaker - Women's Size 7M, Night (Blue Suede) ~NEW~ , TEVA Womens Original Universal Black Sandal Hiking Trail Shoes US 6 NEW!Women Reebok Realflex Athletic Lite V70049 Steel Grey White 100% Original B. New
"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."