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.GEOX Respira Brown Suede Bucklefront Moccasin Style Shoes Size 38 , DANSKO 39 Brown Slip On Comfort SHOES Elastic Inserts 8.5 Clogs Portugal , New Qupid Bee-20 Women Metallic Leatherette Perforated Bow Tie Ballet FlatFranco Sarto Womens Dalton Black Beaded Embroidered Mules Shoes 6 6.5 BHFO 1054WOMENS OPEN TOE BALLET FLAT SHOES BLACK SIZES 5.5 6 6.5 7 7.5 8 8.5 9 10 , WOMENS DANSKO Professional Stapled White Leather SHOES CLOGS 40 , Born Mary Janes Loafer Slip On Brown Leather Strap Womens Shoes Size US 8MBUTTERFLY TWIST NAOMI GREY SATIN LEOPARD FOLDING BALLET FLATS SIZE 10 NIBBorn Womens Brown Leather Slip On Booties W81296 Size 9.5 /41 M/WEtienne Aigner Casual Shoes Womens Sz 7 Blue Leather Moc Toe Loafer-5830G.H. Bass & Co. Size 9.5 Black Leather Flats New Womens Shoes , Asics Gel 1160 Women US SIZE 5 Running Athletic Shoes White Silver Pink (F17) , osiris shoes size 9 new hightopsWomen's Asics Size 9.5 Running Shoes Gel Foundation 5 Sky BlueDESTOCKAGE MULES @ PANTOUFLE MAISON DE L’ESPADRILLE 40 ( DON CAMILLO ) NEUF , SAUCONY JAZZ WOMENS 8 NICE USED DRAB SLATE V-NICE CLEAN see pics-details**Brooks Launch 4 Running Shoes - Women's Size 9.5B - Black , Brooks Women's Racer ST 57 Running Shoes Training Athletic Blue Orange Size 6.5 , Ahnu Womens Montara Waterproof Athletic Trail Hiking Cushioned Mid Boots Sz 7.5 , Elie Tahari Vesuvio Mesh Fashion Sneakers, White/Platino, 9 US / 39 EU Display , Vans Womens Old Skool Black Fashion Sneakers Shoes 5 Medium (B,M) BHFO 3289 , Ryka Silver & Purple Leather & Mesh Lightweight Elate Sneaker 8 NewVERY Rare!!!! CONVERSE Chuck Taylor ALL STAR Sz. 11 Brown LEATHER Plaid PINK oWomen's Donald Pliner Erin Leather Slip-On Year-end Bargain Sale Athletic Shoes , PUMA Women's Vega SL Ballet Flat , NIke Womens Air Relentless 5 MSL Running Trainers 807099 001 Sneakers Shoes , $127 Ahnu Womens Yoga Flex Cross Trainer Shoes, Polar Sky, US 10 , Converse Chuck Taylor All Star Hi Blue Red Womens TrainersReebok Size 8.5 M Trainfusion 5.0 Black Running Sneakers New Womens Shoes NWOBVANS New Era Stars Vault Lady 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."