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.New Shelikes Womens Trendy Fashionable Shiny Glitter Trainers , MANAS Leather Sneakers Size 39 HANDMADE Studded Made in ItalyWomen's Merrell Barrado Brown Chestnut Sneakers Shoes 9 M $99SOFT WALK Women's Tan Leather Sling Back Low Heel Comfort Shoes 11NAndrew Geller Red Flats Shoes Womens Sz 7.5 Dress Shoe with Belt Diamond ShapeNaturalizer Comfort Low Heel Flat Shoes "Daily" Stonewash Denim 9.5M NIBRebecca Minkoff Gavin Light Pink Espadrille Shoes 6.5 Womens Slip On PerforatedMARCO TOZZI Ballerinas Slipper Shoes Court Shoes Dune/Beige NEW , NEW BALANCE 474 TRAIL RUNNING SHOES Women's 7.5 , US Polo Assn Womens Jean/pink Checkered ShoesSANITA PROFESSIONAL SIZE 35 BLACK PATENT LEATHER WOMEN'S 000 , Women's Mesh Hollow Brethable Sneakers Casual Flats Sport Color Stitching Shoes , Womens Jambu Oklahoma Vegan Navy Blue Silver Neoprene Velcro Sneakers Shoes 6.5 , Women's NEW REEBOK WOMENS CLUB MEMT Quality Products Athletic ShoesWomen's Baretraps Mariah Women's FLATS Black Easy To Use FlatsMizuno Wave Inspire 13 Size 9 Women's Running Shoes Turquoise Pink EUCSalmon-Crested Cockatoo Parrot Running Shoes For Men-Free Shipping , Ash Gull Black Womens Shoes Size 6 M Fashion Sneakers MSRP $198 , Nike Metcon 4 Sneaker - Women's Size 8.5 Gray , Skechers Women's Full Circle - Choose SZ/ColorPoetic Licence Women's Going For It New Yellow Polyurethane/Fabric Size 7.5 M , Hoverkicks Lightup Shoes Womens Sports Casual Flats Size 5 Remote Control LEDLuichiny Women's Star Daze , 29 New Nike Women's Lunar Control Vapor Golf Shoes Black Silver 866107-001 7Skechers Women's Size 10 Wide D'Lites Interlude Beige Fashion Sneakers F6-62K-Swiss Women's Tubes 151 L White/Blue/Silver 93371122 New In BoxIRO Novo Sneaker gym shoes size 38 fringe back black suede 8Low Cut Canvas Shoes Girls Daily Casual Sneaker Cute Unicorn Pattern BreathableAltra Intuition 2 Running Shoes SZ 5.5 Womens Athletic Sneakers Pink Gray White , Under Armour Womens Street Precision Sport Low Sneaker Black Size 10 M US
"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."