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.Nine West White and Blue Metallic Slip On Sandal Flat Shoes - Size 7OLSENBOYE Ocairo Womens Size 7M Taupe Fabric Ballet Flats Slip On Shoes , Botticelli Brown Leather Round Toe Penny Loafer Shoes Size 8.5 , Bamboo Mint Green Women’s Flat Peep Toe Sandals Size 9 New NIBWomens Ballet Flats Patent Leather Pointed Toe Slip On Closed Toe Shoes Nude , Sperry Top Sider Womans Flats Size 6.5 Brown Leather Slip On Boat ShoesDr Martens Womens Size 9 () Brown 2-Strap Mary Janes 8065 MIEBenelli Australia Women Size 6 Good Metallic Leather Loafers Nautical Ship Wheel , Klogs Haley Women's Clog Display Model Shoes Slate 7.5 M , Propet Olivia Walking Shoe- Women's Size 8.5, Taupe , SKECHERS 49930 Skechers Vaso Bonita Womens Slip On Sneakers 7.5ESCADA Women Loafers size 7.5 - Green Felt - FLATS Slip-on Leisure Shoes - Gold , Cole Haan Womens Aviannasam Closed Toe Boat Shoes, Red, Size 6.0 , New Balance 610 Blue Gray Trail Hiking Running Walking Shoes Womens Sz 7 MWomen's Clarks Wedge Artisans Slip Ons Size 6.5 (B,M) Casual Solid Black Leather , Teva Big Wall Suede Leather Hiking Trail Athletic Fitness Shoes Women Size 7 , Womens Ahnu Shoes Size 8.5 Lightly Used Clean And Fresh , Keen Purple Turquoise Breathable Mesh Low Hiking Sneaker Shoes Women's 5Nike Sweet Ace Womens Shoes 407992-050 Size 7.5 Black / Purple , BROOKS Raveena 6 Running Cross Training Crossfit Jogging Shoes Women Size 9 , NIKE WOMENS FREE RUN 2 EXT RUNNING SNEAKER ROYAL BLACK 536746 400 NEW NO BOXSkechers 13518 BLACK Go Walk Glow Slip On Athletic Sneaker Shoes Womens SZ 6.5 , Women's fendi espadrilles pre owned Elegant Appearance FlatsAsics Gel-Contend 4 Women's Shoes Indigo Blue/Cosmo Pink/Black t765n-4920 , STEVEN By Steve Madden Womens Neon Sneakers Shoes Creeper Silver Size 7.5Womens NIKE WILD TRAIL Blue OrangeTrainers 643074 403 US 7Adidas Supernova Sequence 6 Woman's White/Orange Running Sneakers Shoes G97983 , Converse CTAS Madison OX Women's Shoe Size 6 Cherry Blossom , ASICS Womens T6c8n Silver/PinkGlow/Lapis Running Shoes Size 7 (365236)Skechers Stretch Fit Women's Walking Shoe 22709/NVCL Size 7 ,
"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."