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.Columbia 3707 Womens Vulc N Vent Orange Canvas Casual Shoes 11 Medium (B,M) , Women's AEROSOLES Silver & Gold Metallic Leather Flat Slip On Shoes Size 8 MNine West Women's Beige Leather Cap Toe Ballet Flat Shoes Size US 8.5 M , CROSS freesail Women's Rain Boots Relaxed Fit , Dansko Black White Gray Silver Metallic Tweed Clogs Shoes 41 / 10.5-11 EUC , Loeffler Randall Eggplant Metallic Satin flats shoes 6.5/ 7B Made in ItalySPERRY TOP-SIDER "AUDREY WOVEN" BOAT SHOES 7M PINK LEATHERDansko Women’s 38 / 7.5 - 8 M Red Burgundy Leather Slip On Clogs Mules ShoesRocket Dog 9 Shoes Sneakers Loafers STOKER Brown Leather C104 , Ecco 38 Gray Loafers Slip On Shoes Womens Leather Footbed 7 , Womens Saucony Nova TR Gray Trainers Size 9M (S928)NEW WOMEN'S TEAMCHEER COBRA WHITE CHEER SHOES FWCF801 SIZE 6.5 , My Style White Mesh Breathable Canvas Slip-on Sneakers Size 6Skechers 'Unbound' active light blue womens 22675 running womens shoe 7.5 , KEDS CLASSIC Canvas Tennis Shoe Sneakers Women's 8 1/2 , Nike Invigor Running Shoes-Women's sz 7 PurpleNike Shox Aqua Blue Pearlescent Running Training Sneakers womens sz 7Easy Spirit Women's Faisal2 Sneaker White Size 11.0 QQUn , New Nike Womens Air Zoom Fearless Flyknit Running Shoes 850426-006 Sz 7.5 multiadidas Performance Women's Sprintstar W Women's Running Shoes With SpikesShoes Lotto Leggenda Iris II Lf Amf W S7665 Sneakers Woman Running Sport Black T , New Puma 188977 16 Fierce Core Paradise Pink Women's Training Shoes 7.5 US , US size 7.5 ladies black leather DB Easy B mules clogs shoes Eur 38 () , adidas Women's Energy Boost 3 Running Shoe Sz 10.5 US , New Balance Women's 996 wr996eb 'Alpine Blue, SIZE 6 US/36.5 EUR,Grey, Suede, DS , VANS ISO 1.5 Wind Chime True White UltraCush Trainer WOMEN'S 8 , New Balance 530 90'S Running Shoes Women's (Size 8.5) W530BNA Pigment / Black , Skechers Women's Millennial-ALL OUT 23543 Black/Multi Memory Foam Brand Newadidas stan smith Black And GoldNEW Puma Clyde Dressed Sneakers Red ,
"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."