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.LADIES EAZE 2 RIPTAPE STRAP SHOE IN BLACK AND TANVince Camuto Ernest Cap-Toe Ballerina Flats, Size 7 BWomens Merrell Apure Dark Brown Leather Loafers US 8 , Mix No. 6 Women's Vigowia Ballet Flats Gold Size 6.5MSofft Women's Slip On Clogs Red/brown Leather Size 7 NarrowWOMEN SHOES MAMA ANDERSON MULES CLOGS Size US 4.5M NEWVintage Salvatore Ferragamo Boutique Suede Flats Wingtips Size 7 Narrow Women’s , Womens Fly London Thea Bridle Open Toe Wedge Heel Summer Holiday Sandals , size 6 M black suede leather ALDO CHELNI loafers shoesNIKE Morgan Mid 2 Shoes Size 6Y White-Pink-Grey BARELY USED , Aerosoles Women's Drive Through Slip-On Loafer - Choose SZ/Color , Vans Authentic Washed Kelp Womens Shoes Sneaker Skater Shoes , New Nike Womens Elite Shinsen Gray Running Shoes Size 12Converse All Star neon green canvas, low sneakers. Women's 6Women's Van's Off the Wall Hot Pink and Grey Shoes Size 6Ryka Women's Tenacity Cross-Trainer Shoe (Silver/Frost) 8 M US2018 New Women'S Students Breathable Spring Shoes Casual Running Soft Sneakers , Nike Womens sz 7 W Wide Revolution 3 Running Sneaker Shoes 819302-002 Grey Hyper , Sam Edelman Dax Women's Walking Athletic Shoes Size 9.5 MTop Moda AD-53 women's vegan slip on sneakers comfort flats shoes weave patternWomen's Vans Slide-On Women's Black/Vans 4LGIX6 New Listing Athletic ShoesWomen's puma shoes women size 7.5 Quality Athletic ShoesSkechers Size 7 Beige Loafers New Womens ShoesPropet Women's TravelActiv Woven ShoeSTEVEN by Steve Madden Women's Hilda Fashion Sneaker - Choose SZ/Color , Women's Karhu Strong Magenta/Berry Brand New Running Shoes F200127Nike FLYKNIT ZOOM US Size 7 Green Blue WORN ONLY A FEW TIMES!! , VANS New Era Northwest Vault Size 8 WOMEN BLACK TOTEMS WHITE NATIVE FISH AZTECADIDAS FOOTWEAR DB1688 QUESTAR BYD W , Avia Women's Avi-Execute-II Running Shoe, White/Chrome Silver/Tickle Pink, 7 W ,
"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."