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.LADIES EAZE NAVY SLIP ON SHOES WITH PUNCHED HOLE DETAIL F3101Clarks Womens Brown Leather Woven Strap Brass Studs Slip On Mules, Size 9M US , New FLEXX Black Suede Leather Loafers Pewter Studs sz 6.5 US /37.5 EUR , Dansko Womens Eartha Suede Slip On Clog - Brown | US 9.5-10 , Jutti Indian Women Shoes Leather Flip-Flops Ballerinas Mojari US 5-10 , Brighton Shoes SPOTZ Silver Leopard Canvas Ballet Flats Sneakers SIZE 8.5 M GUC , Women's SAS Simplify Loafers Shoes Size 8.5M Burgundy Leather Tripad Comfort AA4Soft Walk Women's Shoes Clogs Slip On Size 9 Leather Upper BlackAerosoles Push UPS Penny Loafer Women Shoes Size 7 W AL4411Skechers Womens Knitty Gritty-Knit Bungee Version of The Easy Going-Repute MuleOrthaheel 9M 40 25 Sara Mary Janes womens ladies loafers flats burgundy maroon , Women's Shoes Jessica Simpson MONETAH Slip On Ballet Flats Gold Lizard Metallic , Columbia YL6045-925 women khali taupe comfort sport sandals size 10Bandolino Women's Edition Ballet Flat,Navy,8 M USNEW WOMEN,S UNDER ARMOUR UA W ZONE RUNNING SHOES Gray Blue 1258349-002 Sz 10.5 , Pony Womens Topstar Core White Low Top Sneakers Shoes 10 Medium (B,M) BHFO 3050GUESS Urban Court Tan & White Shoes Sneakers WGPACEE Womens Size - 6MNew Balance Women's Versi v1 Cushioning Running Shoe - Choose SZ/Color , SAUCONY Womens Size 9.5 S19018-6 SPITFIRE Multi Color Sprint Racing Track ShoesWomen's Bass Brown Leather Loafers Surprise Flats , Women's Adidas Gazelle Casual Sneakers Size 5.5 Very Nice!!!NIKE 1983 Women’s 6.5 Waffle Running Sneakers Purple Swoosh Nike’s 831012Brooks Ravenna 7 Running Shoes Pearl Pink Capri Breeze 8D Wide NO INSOLESEd Hardy Original women's low sneakers, new with tags LR107W size 8,9,10Nike womens Air Alvord 10 Black and Pink New with box sz 6 , Nine West Womens Welldone Suede Fashion Sneaker- Pick SZ/Color. , Saucony Grid Fusion 5 Women's Running Shoes Size-11ASH SODA Midnight Black Jogger Sneakers Shoes $235 NEW 40Easy Street Women's Forever , Steve Madden Womens Ecentrcq Low Top Slip On Fashion Sneakers Black Size 11.0 ,
"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."