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.Sperry Top-Sider Bahama Women's Black Boat Shoe 9MBNWOT Women's L.L. Bean mesh moc shoes loafers size 6 M , Daniel Green Women's Karoline Flat,Chocolate,7 M USSANUK BLANCHE PRINTS MELON IKAT FLOWER SIDEWALK SURFER SHOES, US 7/ ~NWTLiterary Womens Girl Bowknot Slip on Loafers Block Heels Patent Leather Shoes OLHotter Size 8 1/2 Women's Pink Strap Slip On Shoes Jl072217 , VERO CUOIO Signature Women’s Black Leather Calf Hair Tassel Loafers Shoes 6.5 , Sperry Top Sider Womens Slip On Sneakers Seaside Metallic Platinum Gold , Tommy Hilfiger Womens Sonya Leather Almond Toe LoafersChaco Womens Size 6.5 Brown Loafers Sandals Pedshed Comfort Walking Casual ShoesWomens Size 8.5 Nike Air Huarache Run SE 859429?002 Grey SneakersWomen Genuine Leather Round Toe Rabbit Fur Mules Flats Oxfords Buckle Warm BootsWomen's Nike Free 5.0 TR Fit 4 Wash Hyper Grape Purple Orange Size 6US - 36.5EURSKECHERS WOMEN FLEX APPEAL 2.0-CHIME IN BLACK/WHITE ATHLETIC SHOES 12894/BKW , Skechers Relaxed Fit Spectrums Showy Womens Slip-on Shoes US-10 22541/CCLMizuno Wave Creation 12 Running Sneakers Size 8.5 Women's Blue 410417Women's San Marina pointure 38 Comfortable Feel Flats , WMNS NIKE FREE RUN+ WHITE-BLUSTERY-BLACK SZ 6.5 [395914-140]Nike Lunar Control Vapor 2 Women's Golf Shoes NEW! Sz 8.5Skechers Go Walk 4 Empower Walking Women's Shoes Size 8 , VANS SK8 Hi Reissue DX (Brushed) Teak/Burnt Coral High Top WOMEN'S Size 7Womens Nike Air Max Thea sz 9 599409 020 95 97 running shoe 90 270Women's Nike Blazer Low SE Premium Casual Shoes Port Wine Sz 8 , Women Red Black Leather Fashion Sneakers Platform Wedge Running Trainers Boots , New Nike Womens T-lite XI walk walking shoes 616696-101 Sz 7 white FREE SHIPPINGNew Balance Minimus 80 V1 Womens Trail Runnnig Shoes Size 8.5 Goretex Grey Red , Saucony Nomad TR Running Shoes Women SIZE 10. Power Grid Nice EUCNike White NZ SHOX shoes - ladies size 8Steve Madden Women's Elouise Fashion Sneaker, Black, 10 M US , Skechers Women's Double up-Shiny Dancer Fashion Sneaker, Black, Size 7.5 68Pn ,
"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."