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.GH Bass & Co. Christina Black Womens Sandals 9M , Steve Madden The Hot Maroon Patent Leather Flats Women's Sz 5.5 MFranco Sarto Womens dalton Suede Closed Toe Slide Flats, Camel, Size 9.5 sGGH , Women's Merrell Spire Emme Black Leather Mary Jane Shoes 6.5 MEARTH BROWN AND BLACK SUEDE MARY JANE LOAFERS 7.5M VERY GOOD CONDITIONSteve Madden Womens Hydes Black Loafer Slides Shoes 6 Medium (B,M) BHFO 2683Judith Ripka Black Leather Snake Emboss Captoe Alberta Ballet Flats 6 NEW , Saint & Libertine Fierce Calf Hair Loafer Leopard Smoking Flats size 8.5SIXTYSEVEN ERIN BLACK LEATHER D'ORSAY SMOKING SLIPPER FLATS Sz 7.5 (Euro 38) EUCNew WOMENS CLARKS Women's MAY IVY 260 63005 LOAFERS Brown LeatherAttilio Giusti Leombruni Ballet Flats Size 40.5 10.5 Leather Cap Toe Chain Women , FILA 2017 Hiking Trail Running Sneaker Women US 8 Leather Synthetic , Womens High fashion Candy color cute sweet Hip-hop sport shoes boots Sneakers , Emu Women's Shoes Silverton Slippers Pink Suede W/ Sheep Fur lining Sz 10 VGUCWomens Summer Buckle Sneaker Sandals Open Toe Shoes Platform Wedge High HeelsMen Reef Slammed Rover Flip Flop Sandal RF2805 Black 100% Original Brand New , Bandolino Womens Hoshi Low Top Slip On Fashion, Grey-gold Jersey, Size 6.0Women Faux Suede High Tops Wedge Platform Ankle Sport Boots Casual Sneakers B72Women's Asics Gel Venture 4 Trail Running Shoes Pink Gray size US 6.5 , DEMO Saucony Natural Series Size 9 US 39.5 EU Women's Running Shoes Yellow/BlueAsics Gel Exalt T379N Running Walking Shoes For Women Size 7.5 , Vans Rowan DX Women’s Shoes Size 10 Skate Casual Sneakers Mint Green Jersey , Saucony Grid Cohesion 11 Running Women's Shoes Size 10 , Asics Womens GEL-Kayano 23 T6A5N Athletic Running Cross Training Shoes Size 11 , NEW - SKECHERS Women's Performance GOwalk Lightweight Slip On Sneaker - US 11 , Skechers Women's GOwalk Lite Splendid Walking ShoeNew Balance Fresh Foam Vongo Running Shoes - Women's Size 7 D, Blue , Mustang High Top With Embroidery Womens Red Synthetic Trainers , Nike Free XT Training Everyday Fit Running Athletic Gym Shoes Black Women's 9 , Nike Size 7.5 Spikes Zoom Rival M 8 Track Multi Use Shoes Blue 806559-401 Womens ,
"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."