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.7820901 LSP30 Women's Shoes Size 7 M Black Suede Slip On Johnston & MurphyGold Casual Slip On Only Party Glitter Closed Round Toe Womens Ballet Flats , Dockers Shoes Women Size 41 Sneakers Flats , Womens WANTED Black Leather Mules Size 7.5 , Isaac mizrahi crocodile croco driving shoes black size 10 fits like a 9 to 9.5INC International Concepts Caleyy7 Espadrille Flats 710, Silver, 8 USMunro American Loafer Horsebit Moc Toe Flats US 8 W Leather Brown M555051Women’s Clarks Brown Leather Side Zipper Loafer, Size 8 ½ MTory Burch Peace Smoking Black Velvet Embellished Slippers Women's Sz 9 M , Geox Respira Woven Patent Leather Black White Slip On Womens Shoes US 8Salvatore Ferragamo Size 6 Cap Toe Flats Black Leather Slip On Loafers ShoesBROOKS BROTHERS Cognac Orange Tassel Women's Driving Moc Slip On Size 8Plus size women Loafers heels Ladies pumps Pointed toe Fur winter Fashion FlockNWOT FUBU Collection Black and Pink Athletic Shoes - Size 9 , Nike? Revolution 2 554900-006 Women's Size 6.5 Athletic ShoesDansko Chrissy Ballet Flats Mary Jane Shoes Size 38 7.5-8 PEWTER A++Womens Barbour Lily Tartan Slip On Warm Lightweight Fur Lined Slipper US 4.5-9.5SAS Women's Brown Leather Slip On Shoes Tripad Comfort Loafers 6 W Free Shipping , Skechers Sz 8.5 Womens Relaxed Fit Memory Foam Slip On Shoes Sandals Taupe TanWomen's SKECHERS Purple & Green Ombre Sneakers - Size US 9ZARA NEW WOMAN White Fashion Sneaker US11, EU42 New AW17 , Vibram Women's Spyridon Mr Elite Running ShoeVans SK8 Hi Slim Leather Bay/True White Women's Skate Shoes Size 5 , Nike Genicco White Grey Pink Shoes Womens Size 8.5 64451-101 , VANS Chima Estate Pro (Herringbone) Light Grey UltraCush MEN'S 7.5 WOMEN'S 9 , Zee Alexis Women's Danielle Woven Fashion Athletic Shoes Gray US 9-9.5 , Women's Sperry Topsider Grayson Rose Viole tCanvas Stk Color Violet , Salomon Cove Women's Chalk Grey Shoes 10MNew Balance Women's Size 8.5D Grey/Aqua/Orange WT410CV5 Running Shoes F2-307Asics GT 2000 Running Shoes Sz 7 Sneakers Black White Silver Womens 2C1 ,
"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."