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.Banana Republic shiny patent tortoiseshell flats Size 6 womans EUCBORN Brown Leather Clog Mule Slide Wedge Shoe Women's 7 / 38 , Naot Sz 39 US Women Leather Black Mary Janes Comfort Shoes , Women's LANDS' END Mocs Brown Suede Loafers Moccasins Slip-Ons 73773 - SIZE 7 HM , Womens Fergalicious Shoes Size 9.5 M FlatsChatelles x Anthropologie Womens Ankle Strap Loafers Shoes Black Size 36 New , NEW Dr Martens Jaime Womens Monk Strap Oxford Shoes 11 Black MSRP$120 , Merrell ColdPack Ice+ Moc WTPF Slip On - Women's Size 7.5, Cinnamon , Womens Ladies Chain & Zip Detail Black Trainers Running Fitness GYM Sports shoesNike Swoosh Ankle High Boots White And Tan Texture Leather Women Size 7 , NWOT Women's Coleman Loyalton Hiking Shoes Size 10 , Skechers Women's Cleo-Dots-Scalloped Collar Engineered Knit Skimmer Ballet Flat , Fashion Womens Graffiti Flower Backless Loafer Slipper Mule Slide New YGABRIELA HEARST BLUE BURGUNDY OXFORDS WINGTIP 36 6Vogue Womens Loafers Sports Running Shoes Athletic Comfort Soft Black DecorationReebok Crossfit Women's Training Running Shoes Size 9.5 Black, PinkMerrell Slip On Walking Shoe Gray Leather Arabesque Gunsmoke Sneaker 8.5Etnies Women's Corby W's Skateboard Shoe, Red/Blue/White, 10 M US , Merrell Womens Sz 10 M-Connect Series Black Gray , Converse Womens Chuck Taylor All Stars Size 7M Black Jeans Triple Zip Sneakers , Skechers Sport SN 11768 Mid Sneaker Chocolate Sweater Fabric Collar Womens Sz 8 , New Women Wild Diva Cala-53 Stars Applique Slip On Low Top SneakerNIKE Women's Wedge Sneakers Dunk Sky Hi Croc Snake 3" Shoes Size 10 SBWomen's size 9.5 Medium New Balance 560 LS7 Women's Running Shoes Sneakers , VANS Sk8 Hi Zip (Overwashed) Blanc de Blanc White WOMEN'S 9.5Brooks Launch 3 Olympic Victory Womens Running Training Shoes Size 7.5 Blue Red , Nike Women's 318463 Ankle-High Fabric Running ShoeNike Womens sz 9 W Wide Revolution 3 Running Sneaker Shoes 819302-002 Grey Hyper , Tsubo Black Sneakers Sport Walking Driving Shoe Womens 11 M Casual Leather , VANS New Authentic Platform 2.0 Summer Mesh Vault Classic Lady Shoes Size USA 7 ,
"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."