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.Calvin Klein RYA Women's Black Glitter Slip On Slim Peep Toe Ballet Flats US 8.5Lugz Ohm Mahogany/Brown/Beige/Taupe Size 6.0 , Women's Corbin Leather Moccasin Shoes 568870 9 BWomens Maj Pow Multi Color Textile Flats Loafers Slip on Shoes Size 6 MWOMENS TOM McANN ZIP UP CASUAL SHOES BROWN SIZE 10 WRockport Womens Loafers Flats Sz 9 M Brown Bow Moc Toe Casual Comfort ShoesJAMBU GRAY ADVENTURE DESIGNS SLIP ON SHOES. WOMEN`S SIZE 9 , Rockport Women's Total Motion Low Wedge Pump Black US 7.5W , Ariat Womens Clogs Brown Leather Closed Back Shoes Style 93946 Size US 7.5 BIndigo Rd. Womens Camryn2 Fabric Open Toe Ankle Wrap Slide, Black, Size 9.0Klogs Missy Women's Clog Shoes Display Model Pink Patent 7 MWomen'S Aetrex Ada Braided Mary Jane Gray40 , Aerosoles Final Exam Wedge - Women's Size 6.5M Black/LeopardNEW Aerosoles Mainland StitchNturn Women’s Black Wedge Loafers US 7 M Shoes A212 , LADIES SHOES/FOOTWEAR - SOA Sandal Flicker natural , ASICS Gel Enduro 9 Running Shoes, #TN8E9, Grey/Blue, Women's US Size 6 , Enzo Angiolini Women's Blue Shoes Size 8.5 , 1836704 Soft Furry Fluff Warm Comfy Men Father Winter Slippers Home Indoor Shoes , LADIES WOMENS POM POM SLIP ON ESPADRILLES FLAT PUMPS SHOES BLACK FAUX SUEDE SIZENike Free Run+ 3 Women's Running Shoe Size 8.5 US 39-40 EURO 510643 500 , Women's Air Jordan Son Of Mars Carmel, Delicate Athletic ShoesWomen's Kampgen Loafers Size 39 Attractive And Durable Flats , New Women's Asics Hyper-Rocketgirl (G553Y) (I16) , Reebok Classic Leather Golden Neutrals Sandtrap/Rose Gold-Chalk BD3744 SZ 6Skechers D'LITES BRIGHT SKY Style 11933/WSL Women's Shoes Size 8.5 NWB , adidas superstar women white metallic size 10Dolce Vita Zalen - Silver - Womens , Women's Easy Spirit Walking Sneakers - Romy - Black/Dark Grey - New in Box!! , New Balance SD100 Silent Hunter Track and Field Spikes Women 9.5 new FREE SHIP , A Must Buy Lucky Green Throwback Nike Air Force 1 Size 8 ,
"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."