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.Aerosoles “Bonus” Women’s Penny Loafers Size 8 Shoes Red Casual Comfort , Streetfly Women's Floral Leather Casual Oxford Shoes US Size 7/ / 245 MM , Footrest womens leather navy flat pumps shoes size 7B , Cole Haan Womens Shoes US Size 6B Blue & Red Casual Moccasins Loafer Memory Foam , Sofft Shoes Women's Mules Pebbled Black Leather Buckle Wedge 2.5" Heel Sz 7.5 M , Womens Sz 6 IMPERIAL DUCK SHOES Brown RUBBER RAIN WEATHER WATERPROOF w/INSERTS , BORN Tan Brown Leather Ballet flats - 8.5LADIES ROCKPORT WARM GREY 2-BAND SLING SHOES "SK62375"CLARKS Women's Size 8M Black Leather Slip On clogs Shoes wedge heels MulesMunro American Womens Beige Snake Leather Loafer Shoe - Size 8MTrotters Womens sizzle Suede Square Toe Loafers , Women's Frye Clogs Mules 7.5 Medium Brown Leather ShoesNEW Women Casual Outdoor Sneakers Fashion Comfortable Shoes White 5603 r_C , VANS New Winston Textile Vault Lady size USA 7 , Womens rivets slip on shoes fashion street loafers round toe board shoes Chz8 , Rampage Cognac retro - vintage style bow wedges wedge 6.5 m twee school femme , New Balance 650 V2 Running Shoes Womens Size 8.5DEasy Spirit~~ Roadrun Leather Walk/Run/Walk 40516 In Box White/Gray~~ Size 8.5M , Salomon Women's X Ultra 2 GTX Hiking Shoe Peacock Blue/Deep Blue/Lucite Green 6MNew! Nike Womens Speedlax 5 Turf Lacrosse White Size 6.5 122P mNew Chaco Womens Kanarra Peach Casual Athletic Running Performance Shoes Size 6Women's TBS Parnak Black Clients First Athletic ShoesGuess Macby 3 Women Round Toe Synthetic Gold Sneakers, 6M , SAUCONY Wome'ns Running Sneakers Tan Sz. 9 , New Balance Women's #WX608v4 Training Athletic Sneaker Shoes Size 8 1/2Skechers Women's Gold Vita Fashion Sneaker US 7 MVans Iso 1.5 Mesh Ultracush Pewter Ballerina Women's Size: 10 (Men's 8.5)Asics Womens Gel Nimbus 16 Running Shoe Sneaker Purple Size 5.5 C433Qadidas Running Clima RideR W Women's Running Shoes Phantom/Red , Brooks Glycerin 10 Pink Gray Mesh Running Athletic Shoes Women's Size 7 B
"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."