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.KELSI DAGGER LEOPARD BETTIE BALLET FLATS SIZE 8M , SKECHERS Memory Foam Women's GRAY Textile Loafers Comfort Slip On Shoes 8.5M US , Spring Step Comfortable & Stylish Red Leather Decorated Wedge Mules European 8MBLOWFISH Womens DEJA Natural Cozumel Linen Pointed Toe Flat US 7M (887837223112)Sam Edelman Circus Cruz Slip On Snake Print Shoes Women's Size 8.5Womens Ladies Over The Knee Thigh High Flat Heel Slouch Suede Long Boots ShoesWomen's Sperry Top-Sider White Canvas/Navy Casual Boat Shoe/Loafer Sz. 9M MINT! , crocs 204623 Womens Citilane Roka Graphic Slipon W Flat- Choose SZ/Color. , Retro Flats Chunky Heels Wing tip Oxfords Womens Casual Shoes Plus Size Autumn , Taryn Rose Crocodile Design Peeptoe size 10m (w/Dr.Scholls gel inserts)VIONIC WOMEN'S BLUE SUEDE FLATS SIZE 9.5 M ROMIT SNUG..NEW Easy Walker Advanced Swiss Walking Shoe Women's 7.5/8 Medium Eco Vegan ShoeEasy Street Women's Kana Mule,Black/Gray Hound,6 2W US , K-Swiss Court Pro II T CMF Women's Sneaker Size 8 Rainbow/ White Tennis ShoesJBU Jambu Womens Keegan Mesh Blue Print Gray Shoe Size 9.5 Wide New , Easy Street Women's Dolores Flat - Choose SZ/ColorBloch Boost DRT Mesh Dance sneakers women's size 10 mWomen's Ryka Rtc Women's Shoes Cheap Athletic ShoesWomen's Converse Revival Ox Womens Shoe Quality Athletic ShoesWomen's reebok classic silver 6.5 Utmost In Convenience Athletic ShoesBrand New Women's Air Max 90 Essential in Multiple Sizes $70 Free ShippingAdidas Originals Nizza Low Sleek Womens Shoes Size 8 Hot Pink Vintage Classic , Vans SK8 HI Velvet Tan/Black Women's Shoes 5BZ968 FRANCESCO MILANO shoes blue paillettes suede women sneakers , NIKE WOMEN'S LUNARSWIFT+ 4 SHOES SIZE 10.5 granite volt charcoal 510790 070$110 Women's Size 9 Yellow Leopard Print Nike Free RN 2018 , Nike Zoom Rival M Women's Size 6 Middle Distance Pink Track Shoes 806559-601 , Brooks Ravenna 8 Running Shoes - Women's Size 8.5 D - NavyWomens Brooks Adrenaline GTS 16 Edition Running Shoes Torquoise Gray Size 9.5 USMerrell Womens Size 9 Ridgepass Espresso/Blushing J247092C Trail Hiking Shoes
"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."