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.Dansko Sela sandals slides. Size 38 / US 7.5 - 8. Blue leather, 2 inch heels , NEW Women's SODA TIME-S Black Slip On Flats Fashion Dress Shoes sz 6.5Dansko Clogs Brown Leather Kelsey Pebbled, Size 40 EU, 9 US, 250 MMWOMENS CALL IT SPRING BLACK GLITTER FLATS SIZE 6 NWB NEW WITH BOX , Talbots Womens Black Leather Flat Loafer Shoe - Size 6MCrocs Women's Kadee Graphic Flat Size 10 , Aerosoles Women's Solid Gray Flats/Loafers, Size 8.5M Stempede W BuckleSAS Simplify Black Patent Leather Croc Loafers Size 9.5S NarrowOak Club Size US 8.5 Dress Shoes Womens Brown Leather Cap Toe BuckleARIAT Clogs Floral Studs Detail Stretch Sides 2" Heel Women's 7.5 M Brown Shoes , Skecher Street Women's Moda-Rhinestone Vamp Fashion Sneaker,Black,5.5 M USBalenciaga Black & Gray Suede Studded & Tasseled Moccasins SZ 36Sperry Top-Sider A/O Quinn Women's FLATS GreyNEW! NIB! Sperry Top Sider PENNINGTON Charcoal White Smoking Loafers Shoes $110 , Women's Athletic Trainers Flat Zip Casual Shoes Sports Shoes Running Sneakers , Men's Lamo Dije Bootie Winter Slippers (Size 13) Dark BrownWomens Red Canvas Shoes Slip Ons Casual Sneakers Kicks Footwear Tennis Flats NewAsics Gel Flashpoint Womens Volleyball Cross Training Running Shoes Size 11.52016 WMNS Nike Air Force 1 Hi SE SZ 10 Black Dark Grey Obsidian 860544-003 , Nike SB PAUL RODRIGUEZ CTD LR (GS) 677375-014 YOUTH SZ: 5~7 WMN SZ: 6.5~8.5 , MNX15 Women's Elevator Shoes OLIVER BROWN Height Increase 6cm by FedEx Fast Ship , Nike 718932 Free 5.0 TR Fit Breathable Women's Running Shoes Training Gym $100 , Reef Women's Rover Low size 9 Black/Charcoal , Womens Nike Free RN Distance 2 Hyper Violet Dark Shoes Sneakers 6.5,7,8.5,9.5 , Skecher Street Women's Side Street-Leather Mid Top Fashion SneakerWomen's Puma Basket Platform Core 364040?02 Puma Black Shoes Sneakers Size 9NIKE WOMEN FLIGHT '13 MID METALLIC PINK GLOW/AQUA BLU /GREY 616298-600 SIZE: 8.5 , Converse Chuck Taylor All Star High Top Women Shoes M9162 - Unbleached White , ASICS Womens - Blue Running Shoes Size 8 (364498)Under Armour Womens Kick Sprint Track and Field Shoes Spikes Cleats Size 9
"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."