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.Pour La Victoire Bonat Flats Pewter Women's 5.5 , ilovebilly - Woman's Flats - Size- 6 () Genuine & New. (I1) , Women's BOC Born Concepts C32041 Brown Suede Ballet Flats 8.5/40 , Luxury Rebel Womens Sari Black Wrap Ballet Flats Shoes 6 Medium (B,M) BHFO 3598Dr Scholls Loafers Womens 6 M Blue Kiltie Tassel Moc Shoes Leather Slip Ons , Naturalizer Women's Sz 8 Red Leather Oxford Style Active Sneaker Career Shoes , Womens Fur Trim Slip On Warm Winter Casual Metallic Comfort Flats Fashion Shoes , CLARKS BENDABLES Women's Shoes Size 8.5 Brown Leather Clogs Block Heel Slip On , KATY PERRY THE LADY SUEDE/PEARLS FLAT SHOES NEW SIZE 7.5Klogs Silvia Women's Clogs Display Model Shoes Black KPR 10 M , COLE HAAN Red Label Black Suede Leather Flats Shoes Womens 7 B Italy , CONVERSE All Star Womens Size 9 /Mens Size 7 Classic Blue Canvas Sneakers ShoesReebok Sublite Women's Shoes Sz 10 Black /Gray/Pink Memory Foam Soles! ?? , Converse Chuck Taylors Burgundy/Maroon High Top W6 M4 , Talbots Women's flats D'Orsay Flats Sz 91/2 NEW w BoxJosef Seibel Womens Black Leather Velcro Clog Sz 39Converse All Star Women’s Fashion shoes 555901F CTAS CORAL OX WHITE Size 6 white , Puma Vikky Mesh Casual Sneakers, Vivid Viola, Women's US Size 9.5TAYLOR SWIFT KEDS SHOE STRIPES AND BOWS SIZE 5.5NEW! WOMEN'S SKECHERS EMPIRE - SHARP THINKING 12418 BLACK/WHITE 127J pmWomen's Nike flyknit lunar 2 women Elegant And Sturdy Package Athletic ShoesWomen's ralph lauren flats 8.5 High Quality And Inexpensive Flats , Skechers Womens Flex Appeal 2.0 Bungee Slip On Shoe, Black/Charcoal/Lavender, 6 , Merrell ALL OUT BLAZE SIEVE J65248 Leather Cut Out Hiking Shoes Sz 8.5 , Nine West Women's Astor Block Heel Pump Silver Synthetic Heels , Saucony Guide ISO Blue-Gray/Lime Running Shoes Women's US 8 (Q2,19)PUMA CELL KINETIC TRAINER SHOES WOMEN'S SIZE 11 , New Balance Womens Walking Shoes Size 8.5 (8245)(H-15) Hoka One One Hupana 2 Women size 5 Running Shoes , Womens gray Saucony Jazz Low Pro Sneakers Size 8 grey teal new ,
"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."