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.Spot On F80252 Ladies Black Microfibre Eyelet Detail Casual Espadrille PumpsDansko Women's Burgundy Leather Slip On Clog Shoes Size 36 Pre-OwnedWomen's Sz.9 SAS Tripad Comfort Loafers Brown Leather Slip On Shoes , Talbots Black Leather Loafer Driving Mocassin Flats Size 9.5 AASperry Top-Sider 9173774 womens Bluefish 2 Eye Boat Shoes size 9.5M brown casual , Women's Merrell Circuit Mary Jane Leather Shoes Sz 9Women's BASS Penny Loafers 7.5W Almost Vintage Pink Leather Flats Moc Toe ShoeIsaac Mizrahi Target 8.5 REBECCA Herringbone Tweed Ballet Flats Slip on Shoes , Clarks Originals Wallabees Brown Suede Chukkas boots shoes size 10 MBIRKENSTOCK Boston Buckle Clogs Sandals Womens US 4 N Closed Toe Black EUC , Sperry Top-Sider Glitter Bliss Sparkly Flats with Tassels Shoes Size 7.5M , Franco Sarto Hudley Loafer, Women's SIze 8 W, Silver , Cole Haan Women's Pinch Weekender Penny Loafer dark spruce Hunter Green 9.5 M , AnnaKastle Womens Pointy Toe Plaid Check Slingback Loafer Flat Shoes , B.O.C Womens Zamora Fabric Low Top Slip On Fashion SneakersBASKETS FEMMES AIR JORDAN FLIGHT POINTURE 36,5 , Finn Comfort Canberra Black Leather Mary Jane Shoes - Women's Size 8.5Nine West Spruce Ballet Flats 943, Light Natural, 6.5 USJ Crew Gold Perforated Leather Flats 9Newton Womens Stability Trainer Running Shoes Sz 9 , Volatile Kicks Womens Wildfoxy Sneaker,White/silver,size 6.5 , New Balance WW813Hv1 Walking Shoe - Women's Size 9 (2E), WhiteSALE Nike Air Max 90 PremiumGenuine Grip Footwear: Women's 8200 Black , Teva Women's Ridge Peak Hiking Shoe - Size 7 - Olive , New Nike Womens AF1 UltraForce Mid Shoes 864025-600 sz 8 Particle Pink , New! Women's Skechers Glider Fearless Slip-On Walking Black/Teal SZ 6 22713 C4 , Converse Chuck Taylor All Star Womens Shoes Size 5 Purple Green Low Top 649962FBRAND NEW Adidas Neo Size 7.5Asics Gel -Fit Sana 2 Blue Bell Runing Shoes 9.5
"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."