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.SAS Womens Tripad Comfort Gold Leather Loafer Shoes 10Black Dap Shoes by River Island, UK Size 4 , Dansko Professional Women's Black Clog 41 EU/10.5-11M US , Tommy Hilfiger Womens Twletya Loafer Size 8.5 Bow Round Toe Flats Brown LeatherTOMMY HILFIGER BABBY WOMEN Womens TWBABBY-BLK BLACK MULTI SUEDE Flats SZ-7.5 , Sam Edelman Felicia Slip On - Women's Size 8W Leopard , Marc Marc Jacobs Womens Shoes Sz 36 6 Black Leather Ballet Flats Casual , Josef Seibel Black Leather Wedge Slip-On Women's Shoes Size 40 US 10 M NEW , COLE HAAN pebbled leather tassel loafers mocassins ivory off white shoes 7.5 BNike Womens Shox Tlx Total Shox Turbo White-Liquid Lime-Silver Sz 9 488344-130Free People Loafer Sable Bollero Scarf by Jeffrey Campbell Black Sz 10Penny Loves Kenny Women's Koi Fashion Sneaker, White, Size 12.0 g88xAsics Women's Hyper-Rocketgirl 7 Running Track Shoes Sz 9 NEW G553Y 3601 , New Balance AT WT590LB3 Womens Sz 9.5 Black Trail Running Athletic Shoes F4-332 , Grasshoppers Womens Athletic Shoes Size 9M Brown Elastic Fastenimg , Easy Spirit Gogo Athletic Sneakers 130, Light Gold/Light Natural, 8.5 US , New Balance 543V1 Sneakers Womens Shoes , Breckelle's ladies fashion sneakers comfort flats women's shoes , Hush Puppies Ekko Gwen Women's Fashion Sneakers Black Crackle , Women's womens saucony size 11 Selected Materials Athletic Shoes , Women's Alfani Aleaa Women Ballet Flat Beautiful Design Flats , Women's STUART WEITZMAN Walkmyway Metallic Espadrilles Colours Are Striking Flats , Skechers Performance Women's Go Step Lite-Indigo Boating Shoe , Wmns Nike Air Max Zero QS Grey Blue Women Running Shoes Sneakers 863700-001 , Adidas Tubular Shadow Women's Shoes Grey Three/White AC8331 , Newton Running Boco Sol - Blue - Womens , Nike Womens Air Presto Jacquard Premium Shoes Sneakers 10 US 42 EU RunningWomens Under Armour Flow RN GR II athletic shoes 7.5 blue turquoise 1268378 467 , Womens Sz 8.5 Nike 6.0 Orange/Mint Green/White Athletic Shoes No InsolesNike Air Blazers 316482-161 White Red Paisley Pattern With Dog Size 8.5
"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."