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.Cole Haan Slip On Shoes Muted Sandy Brown/Ochre Suede & Mesh Size 6B , Alfani Black Croc Embossed Faux Patent Step n Flex Flats Allegra 8.5MSTEVE MADDEN WOMEN'S FABRIC LOAFERS/SNEAKERS, BLACK, US 6 , DEXFLOW COMFORT White & Black Patent w/ Capped Toe Classic Ballet Flats 7.5 NEWIsaac Mizrahi Womens Gray Shoes 6 , N.O.S Womens P. W. MINOR TRAVELER BUCK DR Orthopedic Diabetic Shoes Size 9.5AAAtavon Womens Black Leather Mary Jane Flats 9B Excellent Used Condition , ***NEW*** Gola Women`s Jogger , Nylon/Suede Size 6 U.S.Women's Size 9 SAUCONY Ride 6 Running Shoes 10200-5 Power Grid Purple Plum , Adidas Women's Adistar Racer Sports Runners Sneaker Shoes Black Gold Size 8 , Chic Sequins Women Flat Block Heels Pumps Slip on Pointed Toe Bowknot Bead Shoes , Women's Real Leather Rabbit Fur Lined Slippers Flat Metal Slip on Casual ShoesSperry Top-Sider Womens Brown Leather Boat Shoes Size 7.5 Gold Sparkle Slip Ons , Woman's Nike Flywire 8.5 Grey & Teal Running Shoes , Dr Andrew Weil Silver White and Pink Specialized Walking Shoes Size 10W NICE! , ASICS GEL ONITSUKA TIGER FASHION SHOES WOMENS SZ 7 OLIVE GREEN PINK ATHLETIC EUCAsics Gel-Exalt 3 Running Shoe - Women's Size 7.5 - Gray/Blue T666NConverse Andy Warhol Collector Brillo Chuck Taylor High Tops All Star Shoe sz, 7NIKE YOUTH SHOES SB STEFAN JANOSKI (GS) DEEP ROYAL BLUE 525104-402 Youth Sz. 5~7Golden Retriever Print Slip Ons For Women-Express ShippingWomen's Adidas Gazelle Casual Sneakers Size 9.5 Very Nice!!! , Women Adidas CQ1065 Adiease Running shoes white red Sneakers , Zumba Energy Boss Shoes - Pink A1F00106 , Amazon Red Headed Parrot Print Running Shoes For Women-Free ShippingNIKE LUNAR GLIDE 7 WOMANS Sz 8 Cool Gray , Womens Size 8 Converse Chuck Taylor Sneakers Gemma Fiberglass 555841C , Vintage 90s New Fila Womens 7.5 Hilly Hiker Hiking Camping Boots Shoes Brown , Vasque Gore-Tex -Women's-Mantra 2.0 GTX Hiker - Canteen/Orange Peel -7071 SZ 10Womens Asics Gel Flux 2 Running Gray Pink Size 9 , WMNS NIKE FREE TR CONNECT 2 Hyper Cobalt/ Deep Royal Blue -638680 400- RUNNING ,
"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."