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.Madeline Stuart Brandy Black Slip On Comfort Loafer Shoes 10W -Wide- , White House Black Market "Jamie" Women's Black Fabric Jeweled Ballet Flats Sz 9M , NEW GENUINE GROSBY JIFFIES WOMENS LADIES BALLET DANCE FLAT SLIPPER BLACK SHOESSkechers Womens White Leather Fashion Sneaker Shoe - Size 7.5MNEW WOMEN'S COMFORTVIEW SNIP-TOE BALLET FLAT (SHOES) BR. RASPBERRY SIZE: 7 1/2 WWomen's Steve Madden Chaufur Black Sparkly Flats Size 6 MNina Joplin Loafers Womens Size 7.5 Blue Low Heel Leather Slip On Shoe-5045New Women Refresh Stacy-02 Suede Round Toe Chain Embellished Slip On Ballet Flat , Women's Skechers 14710/NVY Go Step Lite Persistence Navy , BALLY OF SWITZERLAND soft leather brown penny loafers Shoes 8 MNEW BORN SEBRA WOMENS BLACK LEATHER D74603 FLATS SHOES SZ 8.5 MWomens Buckle Slip On Walking Lightweight Padded Sports Shoes Trainers , Cute Girls's Bling Glitter Sequin Slip On Cartoon Sneakers Casual Loafer ShoeSkechers 12418 NVPK Women's Empire - Sharp Thinking Walking Shoes [146A] , NEW $54 Womens Converse Chuck Taylor All Star Ox Shoes, size 10Woman’s Nike Roshe Run Size 9Women's New Balance brand White Tennis Shoes, Size 8 1/2 , Fair ConditionBrooks Adrenaline GTS 13 - Running Training Athletic Blue/Gray Women's Size 9.5DVans Ward Hi Women’s Canvas Shoes Sneakers, Black/White, Size; 5.5 , Kenneth Cole Womens Kl06090pa Black Fashion Sneaker Size 7.5 (9934)New Balance 630V5 Sneakers Womens ShoesNew Puma 364092 02 Basket Platform VR Puma Black Women's Casual Shoes 7.5 US , Aerosoles Women's Midpoint Ankle Cuff Sandal Taupe Faux Leather Hook and LoopNIKE WOMEN'S AIR ZOOM ELITE 8 SHOES SIZE 11.5 orange black yellow 748589 800Womens NIKE SHINSEN FLY FORM Blue Textile Trainers 832509 417 , Merrell Moab Ventilator Mid Hiking Outdoor Athletic Boots Walnut Wmns's Sz8.5 B5 , Nike Air Max Team ST Running Training White Navy Blue Sneakers Shoes Womens 6.5SKECHERS Womens Black Shape Ups Fitness Walking Sneaker Size 10 11809 OriginalsMizuno Wave TORNADO 6 White Volleyball All Court Tennis Shoes Womens 7.5 VS1 , Altra Intuition 2 Running Shoes SZ 5.5 Womens Athletic Sneakers Pink Gray White
"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."