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.Womans Mary Janes black shoes sz 5 , COLE HAAN D13816 K3 WOMEN'S BLACK LEATHER & SYNTHETIC MOC SNEAKERS 6.5 B , Restricted Modcloth Tartan Black Red Green Plaid Leather Ballet Flats 6 Retro , Akira Slides New Shoes Women Size 6Women's Clarks Dressy Flats Sz 7 ExcellentYellow Box Women's Boronia Sandal Brown *Mismate* Size Left 7.5M / Right 8M , Iron Fist Don't Pussy Foot Leopard Face Print Women's Ballet Flats - US SizeDr. Scholl's Advanced Comfort Series 6W black pull-on loafers shoes. Side zipper , World Blend DARK Brown Leather Comfort Shoes Slip On Loafer US 10 Women , Easy Street Women's Splendid Flat, Brown, 6.5 W USLadies Suave Versatile Flats - LucyClarks Cloudsteppers Dark Brown Sillian 20932 Paz Slip-On Size 9M , Ladies Easy B Slip On Canvas Shoes HilaryMIA Womens kirsten Fabric Pointed Toe Loafers, Black bouquet, Size 6.5 sC4B , Easy Spirit Womens Traveltime Leather Closed Toe Slide FlatsCLARKS Artisan Women's Shoes Clogs Mules Low Black Leather Size 8.5M , NEW Clarks Slip-on Loafers - ASHLAND BUBBLE - BLACK SNAKE - 9 M , Clarks Leather Slip-on Shoes - Ashland Lane PICK SIZEGUESS Ballet Flats 7 Brown Monogram , Women's Dansko Madras Plaid Casual Cool Loafer Sz 40/9.5 MINT! , Women's Converse Chuck Taylor 'Shoreline' Sneakers 6M Athletic Navy , Authentic Fenty Black Puma fur slides Rhianna Empty Storage Gift Shoe Box BlackNike Free XT Women's Size 11 Everyday Fit Running Shoe , ASICS GEL KAYANO 22 RUNNING SHOES, WOMENS SIZE 10 BLACK GRAY CORAL EUC!!Women's Puma NTRV Great Varieties Athletic ShoesNike Cortez Classic LX Velvet White Womens Size 9.5 , NIKE WOMENS LODEN SZ 6.5 DARK STUCCO RIVER ROCK GUM WHITE OLIVE ROSHE 896298 006 , Reebok RealFlex Racer Blue Running Cross Training Sneakers Shoes Womens 11Women's Puma Blaze of Glory Decor 36053201 White New In BoxBrooks Adrenaline GTS 16 Women's Running/Walking Althletic Shoes SZ 7.5M Gray ,
"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."