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.BANANA REPUBLIC Brown Leather Ballet Flats Shoes sz 8Womens Rocket Dog shoes - C225 12482 - brown - size 8DC Women's Villainess White/ Black Skate shoe 9.5M , American Eagle Outfitters BLACK SHOES WOMENS SIZE 6 1/2 , MERRELL " Encore Emme" Womans Size 8 brown suede shoes- ExcellentNew LAURA SCOTT 'Hunter' Black Leather Slingback Braided Flats Size $29 , Sperry Top-Sider Women's Green Plaid Canvas Upper Boat Shoes 11 MSanrio Hello Kitty Women Sz 6 Flat Shoe Hello Kitty Logo White Pink Black SlipOnSplendid New Jaime Gray Womens Shoes Size 10 M Flats MSRP $98FRYE QUINCY BOAT SHOE 70150 GRAY LEATHER Size WOMEN'S 8.5 M , Madden Girl Womens Comicc Fabric Round Toe Loafers, Black/ Fabr, Size 9.0 9oz8 , Crocs Womens Freesail Clog Navy 9 M US , Nine West Women's Umissit Fabric Ballet Flat, Black White/Black, 6 M USWaldlaufer 5.5 Henni Black Womens US 7.5 Leather Casual Mary Jane Comfort ShoesSteve Madden Women's Phase Ankle-High Leather Fashion Sneaker , New Women Authentic American Heritage SO Flash Sneakers Shoes Size 10 - Blush , Women's Nike Juvenate New Product Athletic Shoes , Women's NEW BALANCE Sneakers (Size: 6) Strong Resistance To Heat And Hard Wearing Athletic Shoes , Women's Balmain Sandals High Quality Flats2005 NIKE AIR FORCE ONE OLIVE PINK GUM BOTTOM SZ 11 W 9.5 M 308038-3611 MAX SP , Nurse Mates PENNIE Women's White Leather Slip On Nursing ShoesHoka One One Challenger ATR 2 Woman’s Size 6 EU Size 37.5 , New Balance Women's W680V3 Running Shoe , ZARA floor contrast Hoody US6,EU36 LightWeight black fashion sneaker 6720/101Demonia Women's Creeper 304 Wedge Oxford , Nike Air Zoom Revive Womens Tennis Sneaker Cover Sz 5 5.5 Pink White Swoosh Shoe , Vivobarefoot Primus Lux Grey Opal Sneaker Running Shoe Womens 36L US 6 England , 12981 Black Skechers shoes Memory Foam Women Slip On Bungee Comfort Casual Mesh , Easy Spirit Women's Faisal2 Sneaker Pink Size 8.0 , New Balance Womens Wl515ifb PinkClay/BleachedSunrise Running Shoes 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."