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.Dexter Womens Light Beige Suede Mocassin Slip On Size 8 ShoeChristian Siriano For Payless Women's Pointy Toe Slip on Flats ShoesLands End Moccasin Style Suede Slip-On Loafers, Dark Brown Size 7.5 Med , Claudia Ciuti Black Suede Square Toe Loafer Shoe Size 9 , Privee Brown Faux Fur Ballet Flats Size 41 11 , Eileen Fisher Tour Flats Black Espadrilles Nubuck leather Sz 8Etienne Aigner 40 9M Sempest brown suede womens ladies moccasins loafers flatsSAS Penny Loafer Shoes Womens Tripad Comfort Pinched Mock Toe Leather Sz 9 Black , Clarks Collection Womens 8.5 Slip On Shoe Brown Leather Casual Soft Cushion , Trotters womens shoes 7 N narrowNIB New Women Merrell Dassie Buckle Shoes Espresso Brown Size 6.5NEW SPERRY TOP-SIDER A/O PURPLE WOOL PLAID BOAT SHOES WOMENS SZ 7 $85.Volatile Size 7 Camo Flats Leather Brushed Hair New Womens Shoes , BUCKETFEET Peacock Womens Shoes, Black/Green/White, 9 , Skechers Goldie - Diamond Darling Silver Womens Fashion Sneaker Size 9M , Womens Size 6.5Y Nike Air Force 1 Low White/Purple/Lime Green , Skecher Street Black Shiny Dancer Shoes Size 8New Reebok Womens Rbk Print Run Prime Ultk Blue Running Shoes Size 9 , ** Ryka Henley Fabric Slip On Sneakers, Women's Size 5 M, Teal/Pink NEWAsics Aqua & Pink Mesh Athletic Running/Walking Sneakers Shoes Size 7.5!Nike Gree OG '14 Black Lime Grey Suede Womens Trainer Shoes BootsWomen's AVERY B CUIR MARINE Great Varieties Athletic Shoes , Puma Match Lo Basic Sports 35754314 FemmeNew Merrell J09654 Bare Access Flex Paloma Women's Running Shoes 8.5 USASICS Women's GT-2000 5 Running Shoe, Pink Glow/White/Dark Purple, 6.5 M USDutch Warmblood Horse Christmas Running Shoes For Women- Free ShippingPUMA Women's Suede Heart Reset WN's Fashion Sneaker - Choose SZ/Color , INC International Concepts Womens Sammee5 Fabric Low Top Slip, Black, Size 8.5 q , NEW BALANCE SIZE 6.5M WOMENS TRAINING RUNNING SHOES LIGHTWEIGHT GRAY ORANGEPUMA Appeal Women's 180557 02 White/Teaberry Running Shoe Sz. 7 1/2 MINT! ,
"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."