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 Womens SODA RENEE Beige Knit Slip On Flats Loafers Dress Shoe SZ 9 , MERRELL *Plaza MJ Saddle*Chocolate Brown Leather/Suede Mary Jane's-Size 10.5Tommy hilfiger Pointy Patent Ballet Flats , SAS Womens Shoes Tri Pad Comfort Brown Leather Slip On Loafers Size 9.5 WMERRELL Sailix Ballet Tan Women's Shoes Size 6.5 Slip on J89308 EUC , New Paul Green 'Townsend' Flats, Zipper Cap Toe, 6 WomenWomen's Nine West Fashion Sneakers - Oleandro - Off White/Black - New!! , Franco Sarto Womens Porter Leather Closed Toe Mules Black Size 7.5 gvqtElectric Karma Shoes Brown Penny Loafers Womens Size 7 NEWWomen's Cole Haan D16112 Size 8B Loafers Clogs Shoes Pink Leather Casual B10Dr Scholls Brown Ballet Flats Size 7 Perforated Floral Buckle Round Toe Slip OnAttilio Giusti Leombruni Red Shimmer Suede Cap Toe Patent Flats sz: 38 | US 8 , Adrianna Papell Size 6 M Linda Flats Black Leather Loafers New Womens Shoes , 100% Authentic Tory Burch Pennie Low Heel Saffiano Leather Brown Loafer Size 8 , Born Womans Flats Size 8 39 M/W Brown Leather Buckle MulesMephisto Runoff $260 Air Jet Women's Oxfords Shoes Size 6.5 Nubuck Leather BrownWomens Skechers shoes - white - size 7.5JBU by Jambu Women's Cherry Hill Flat , Asics Running Shoes Silver TN8E9 Womens 7.5 FIT Shoe Stunning Barely Used 39Men's slipper by FlyFlot - slipper Shoes - Cord PU sole - Gray , ASICS GEL TITANIUM WOMEN'S ATHLETIC RUNNING SHOES SIZE 9.5 Green GRAY T3B6Q , FOOTJOY SUMMER-SERIES WOMEN'S COMFORT GOLF SHOES SZ 6M VERY GOOD+ CONDITIONNEW Spring Step Women's Mitzy Fashion Sneaker Navy Suede 39 EU/8.5 M USDance Class Women's C501M Character Shoe, Caramel, Size 4.0Women's CLARKS shoes Size 7M Superior Quality FlatsMerrell Riveter E-Mesh Womens Trail Running Shoes Athletic Sneakers New J98860Adidas Women Lux Clima Running Shoe Aero Pink/Hi-Res Green/Black CG5110 sz 10.5 , Converse Women's Shoreline Slip on Sneaker - Choose SZ/Color , $75 Women Keds Kick Purple Ditzy Floral Printed Canvas Sneakers Size 6.5mSkecher Shape Ups Women's 7.5 Tan Suede Leather Walking Rocker Toning R5-S5 ,
"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."