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 Anne Michelle Flat Shoes with Bow Trim Style F80183 , Nurture Brown Mary Janes Size 7M , Lauren Ralph Lauren Womens 7M High Heel Wingtip slip on loafers shoes Black Y621**Dr. Scholl's Giorgie Faux Suede Ballet Flats, Women's Size 7M, NavyBorn Horse Bit Black Leather Loafers Slip On Shoe D05003 Womens Size 7.5 MTOD'S Maroon Suede Moc DRIVING Shoes Penny Loafers Size 7.5 AS ISYves Saint Laurent Sz 7.5 Brown Suede Pumps Crisscross Straps Low Heel Italy YSLCalvin Klein Women Leather Suede Lunasi Slip On Loafers Size 7.5 Dark Cranbe , Derby Les p'tites Bombes GARANCE vernis noir Nouvelle CollectionTory Burch Silver Metallic Leather Floral Blossom Toe Ballerina Flats Sz 8 NewNew Women's Dansko Loretta Black Platform Oxford US 6 , SAS Womens Shoes 8N Narrow Metallic color Loafers Leather Penny Loafers Slip on , Women's Sperry Top-Sider Tan Leather Boat Shoes 8M , CLARKS Collection Women Side Zip Walking Shoes Size 7.5 M Brown Leather , Fabi Croco Textured Pointy Toe Leather Flats Italy Signature details logo**Merrell Around Town City Moc Knit Slip On Shoes, Women's Size 9, Black/White , Asics Gel Exalt 2 Women's 6.5 Pink Grey Athletic Running Sports Shoes T4C6N , Impo Stretch Regis Womens Open Toe Red Strappy Wedge Sandal ~ Size 6 1/2 M. , Womens Ladies Woven Shoes Slip On Multi Colour Mary Jane Elastic Upper TrainersNew Balance Vazee Rush Gray Leather Running Shoes Women’s Sz 7.5 B , Skechers SKCH 3+ Womens US Sz 7.5 Hidden Wedge Ankle Sneaker BootsNike Womens White Lunar Air Cross training Shoes Size 10 B10 , Asics T4H7N Gel Kayano 21 Black Women Size 11 Running Shoes H2 , Women's Nike Lunarglide 8 Running Shoes - Black/White - NIB! , Adidas Zx Flux Women's Shoes Size 6.5 , Leta Slip On Sneaker by Dr. Scholl's in Black size 9 , Skechers Women's Microburst - Greatness Grey Memory Foam Sneakers Shoes Sz: 7 , Puma New Elemental Gray Womens Shoes Size 9 M Athletic MSRP $100 , Qupid Sz 6 Pink Satin Rabbit Fur Pom Shoes Reba-94C New NIBKEDS Taylor Swift Champion Lazer Lights White Womens NEW ALL SIZES ,
"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."