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.Audrey Brooke Black Paris Flats Size 6.5 MPretty Leather Blue with flowers Flat Shoes (Selena) from Hush Puppies - size 7 , Pierre Dumas Womens Shoes NEW $40 Moni-28 Black Patent Ballet Flat 6 M , Savannah Ladies Sandals F0795 Pink UK Sizes 3x8 (R21A)Calvin Klein Lucy 5.5M Black Leather Almond Toe Penny Loafer Flats FLAWED , naturalizer Gadget Loafer Flats, Gold, 9.5 US / 39.5 EU , Cole Haan Womens SZ 8.5 AA Brown Basket Weave Woven Leather Slip On Loafers #G88New Hotter Comfort Concept Red Maroon Shoes Adjustable Strap In Sz 7 EnglandLeather Women's Round Toe Rivet Strap Decor Slip On Loafers Flats Shoes NewSkechers Microburst Perfect Note Womens Ballet Flat Memory Foam Shoes , Aerosoles Stitch N Turn Limbo Bootie Mocassin Black Suede Ankle Boots Size 5.5M , Acorn Women's Acorn Moc Tex/Polar - Chinchilla - XL , Women's REPORT 227005 black / white geometric fabric espadrilles sz. 8Merrell Vibram Women Hiking Walking Shoes Black Silver Gray Size 7.5 USCONVERSE CTAS Madison OX Women’s Size 6 Black Canvas Sneaker Shoes F3-908sn231 CHAMPION women memory foam insole black shoe size 8 / 50% of retail!!!!NIKE WOMENS RUNNING / WALKING SHOE PINK / WHITE SIZE 7ASICS GEL ENDURO 7 Running Trail GRAY Green Womens Size 7.5 , Women's NEW LUMBERJACK WOMENS SNEAKERS Online Outlet Store Athletic Shoes , Women's LA GEAR Sunrise Canvas Black Easy To Use Athletic ShoesWomen's Nike Court Force Women's 7 Excellent Quality Athletic Shoesadidas Women's Cloudfoam QT Racer Running Shoe - Choose SZ/ColorPin Up Couture Women's Siren 09 T-Strap Slide Lavender Faux Leather Heels , Diadora GAME ARCHIVE - White - WomensFila Women's Memory Panache Training ShoeOn Cloud Running Shoe- Women's Size 8, Jade , Nike Air Extreme Volley Womens Volleyball Training Shoes Sz 15 (B234) MaxAir , NIKE SIZE 7.5M DART 12 WOMEN'S DARK PURPLE WHITE LOGO BRAND NEW RUNNING SHOE , Reebok Womens Royal Alperez Dash Sneakers Caribbean Teal White Size 8 NewNike Women CK Racer Size 7.5 ,
"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."