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.Womens Ladies Platform Wedge Heel Sandals Espadrille Studded Summer Shoes Size , M.P.S. Silver And Black Sequin Slide Flats ShoesLadies Womens Studded Western Ankle Boots Cuban Heel Vintage Cowboy Shoes Size , BORN Women's Leather Mules Clogs Slip On Shoes Womens Size 7 US / 38 EURMUNRO American, Women's Size 9 A, Tan Leather Slip On Mule, Lizard Print ToeBorn Womens Mules Brown Leather Embossed Elastic Side Slip on Shoes Size 7M , BellaMarie Angie-28 Classic Pointy Toe Ballet Flat Shoes Champagne Gold GlitterWomens Drew Mary Janes Black Leather Diabetic Shoes Size 11.5 New , TATAMI Women's Size 48 Beige Taupe Buckle Leather Ballet Flats Shoes Spain c9New Steve Madden Karry Rhinestone Perforated Coral Suede Flat Shoes sz 9.5 , Rampage Women's Insight Flat (9, Black)Easy Street Women's Kana Mule,Black Suede,7 2W US , Skechers Comfort Air - Just A Lil Knit Navy Womens Sneakers Size 9M , **Puma Basket Heart Patent Sneaker, Women's Size 9, Red , GLOBE Mace Hi Tops Skateboard GRAFFITI PAINT Athletic Sneakers Womens Shoes Sz 9Tommy Hilfiger Size 7.5M Gray Fabric Green Suede Active Sport Causal Tennis Shoe , Asics GEL-Pulse 7 women's 9 gray yellow green running shoes trainersWomens Worn Once Too Cute Brown Champion Casual Shoes Size 7/ Gifts For HerSkechers Shape Ups Walking Fitness Women’s Shoes Size 10 White Silver Pink 12350 , ASICS GEL GT- 2000 RUNNING SHOES / MULTI COLOR ( SIZE 8 ) WOMEN’S , WOMENS REEBOK INSTAPUMP FURY CELEBRATE SZ 7-10 BLACK CHALK AQ9079New Balance Womens Size 6 CM620NNV Shoes 620 , GUESS Factory Women's Dani Glitter Wedge Sneakers,NIB.6.5 , disney evil queens inspired HIGH TOPS HAND PAINTED MADE TO ORDERNWT Women's Adidas Gazelle Velvet Vibes Pack DB0164 Black Raw Pink Shoes , Naturalizer Women's Carly Slip-On Sneakers AB4 Deep Sapphire Blue Size 4M , Demonia Women's Cramps 03 Ankle StrapSAUCONY Womens HURRICANE Sneakers 9.5 Running Shoes PRO GRID Arch Lock TRAININGVintage L.A. Gear Womens Sneakers Size 7.5 Brown Shoes Retro 80s 90s Athletic , REEBOK FREESTYLE HI COLORS LIME GLOW GREEN WHITE WOMENS SIZE SNEAKERS BS9369 ,
"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."