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.Bijou Black Patent Criss Cross Straps Silver Buckle Ballet Flats NewNEW , Skechers BOBS Plush Robins Egg Slip On Shoes, Women's Size 9, BlueBellini Womens Formosa Pointed Toe MulesPhoenix Embroidered Shoes Fashion Woman Single Shoes Flats Dance Shoes by Ela...Sesto Meucci Womens Brown Woven Leather Flat Loafers 9 Narrow Made in Italy Shoe , Dansko Brown Leather Clogs Shoes Sz 38/L7.5-8New Zara Shoes Contrast Sneakers Size 6 Second item ship for freeCole Haan Air Tali Black Rain Slip On Wedge Loafers Size 6.5 BGood condition! 41 Dansko wool comfy 1.5" heel loafer slip on casual shoesStuart Weitzman Womens Sugar Blue Espadrilles Flats 10 Medium (B,M) BHFO 8717 , Women's Aerosmith Black & White Canvas Sneakers US Size 10Women's Shoes Running Walking Breathable Casual Sneakers Athletic Sports Outdoor , Merrell Women’s Siren Sport 2 Sport Hiking Shoes Vibram Soles Size 8Womens Nike Max Air Black & Pink Running Shoes Size 7.5Dolce Vita Women's Tala Fashion Sneaker, Palm Print Canvas, 7.5 UK/7.5 M US , adidas VS SET MID - White - WomensNew Balance Womens Purple Running Shoes Sneakers 5 Medium (B,M) BHFO 1658DC Skateboard Shoes, Women's 'REBOUND HI LE' sneakers, leather upper, size 10 , GUC Womens COLUMBIA "bugabutte" Gray Leather/ Puple 9.5 hiking trail omni grip** New Balance W890EE Women's Sneakers - Black - Size 5.5 B , Women's Vans Womens Shoes Diversified Latest Designs Athletic ShoesAsics Tiger Ult Racer Running Women's Shoes Size 8.5 , Merrell 1six8 Linna Strap AC+ Women's Size 7 Black 25%OFFFila Size 8.5 Gray Slip On Sneakers New Womens Shoes , adidas CloudFoam DAILY QT MID - Navy - WomensNEW Saucony Grid Web Memory Foam Running Shoe s15291-4 Teal Size 7NIB Skechers EZ Flex 2 Fascination Slip On Loafer Shoe Navy Blue Womens Sz 8.5 , Nike Air Zoom Fly 2 Women Hot-Lava Black Glow Running Shoe Sz 8 EUC!REEBOK NEW CLASSIC LEATHER AND SUEDE BLACK AND GREY WOMEN ROYAL CL JOG TRAINERSWomen High Top Casual Sport Athletic Short Boots Hidded Heel Pu Leather Shoes Sb ,
"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."