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.Taryn Rose Shoes Cream Leather Black Patent Comfort Shoes PAISLEE Women's US 9M , Sperry Top-Sider 'Largo' 9835067 Madras Plaid Canvas Ballet Flats Size 7.5Sperry Top-Sider Women's Blue Insulated 2 Eye Boat Shoes - US 7 M , Womens Size 6.5M Lands' End Green Suede Leather Mary Janes , ** Skechers Luxe Slippers - Women's Size 10 BrownMojari Handmade Leather Women Shoes Flip-Flops Ballerinas Indian Flat US 6/9 , Ralph Lauren Camila Chambray Gray Suede Driving Moccasins Flat Size 6.5 EUCNaturalizer Chestnut Brown leather Mary Jane Sz. 6M MINTY! , MINNETONKA Women's 7 Brown Moose hide Leather Loafer Moccasins Driving ShoeAetrex Stretch Women's Brown Leather Wedge Mary Jane Loafers Size 9 S563 , BOC Born Concept Women's Brown Pebble Leather Slip On Clogs Shoes Mules Sz 7M96 FILLING PIECES Foxtrot Nude Leather Low Top Sneaker Women Size 40 M , New Etnies Womens Scout Xt Black/Pink Running Shoes Size 5 , NEW Womens SPORTO Slip On Gray Active Mule Walking Shoes Size 10 , PUMA VOLTAIC WOMENS 8 EUC SUPERCLEAN RED WHITE CREAM see pics-detailsNike Free Flyknit 4.0 Sneakers Running Shoes Women's Size 7.5 Hot Lava , Women's Nautilus Women's N1393 Trendy Athletic ShoesWomen's womens naturalizer shoes size 71/2 To Adopt FlatsPUMA Women's Rebel Mid WNS Velvet Rope BL Sneaker - Choose SZ/Color , New Disney Block Party Bash Women's Athletic Sneaker Shoes Size 8 Costume Studio , adidas Alphabounce EM Women's White/Talc/White BW1196 , Skechers Summits Light Dreaming Athletic Women's Shoes Size 7.5 , Women's Nike Free TR 6 Training Shoes NEW White/Orange, MSRP $100 , Reebok Royal Ultra Shoe Pale Pink Suede OrthoLite Sneaker Size 7.5Footprints by Birkenstock Darlington Sneakers Size 39 US 8 - 8.5NEW BALANCE W575LP1 WOMEN'S GREY/PINK RUNNING SHOES SZ 6.5 , NEW NIB VANS WOMENS BLACK 5.5 PAITYN SHOES PLAID RED ROCKABILLY RARE , Nike Zoom Rival M 8 Womens Sz US 9.5 Sprint Track Spike Blue White 806559-401Nike 10M Dunk Low Vivid pink fashion sneakers womens ladies basketball shoes , New Balance 920 Running Shoes Women’s Size 6 B US Near Mint Condition
"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."