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.Ballet Flats Fergalicious Taupe Neubuck Uppers Flat Shoes by Fergie Size 6 NWOBMerrell Ladies Clog Air Cushion Silver Gray Size 6 Slip on MulesPRIVO by CLARKS GRAY/BLACK LEATHER SLIP ON LOAFERS WOMEN'S SHOE SIZE 10 M , Clarks Shoes Womens 84630 Brown Leather Slip On Loafer Casual Wedge 9.5M , Loly in the Sky Critter Fix Sneakers Tennis Shoes Sz US 9.5 Fox Head Print TanKaren Scott Samor Womens Slip On Wedge Heel Loafer Shoe Brown Synthetic Size 6Qupid Womens Spyrock -11 Low Top Slip On Fashion SneakersSkechers Womens Outdoor Lifestyle Brown Bronze Hiking Fishing Trail Sport SZ 8.5 , Rebecca Minkoff Vicky Women's FLATS Black/White WovenAutumn Platform Shoes Woman Slip on Casual Women heel inside mujer zapatos redWaldlaufer Etta Hegli Black Womens Patent Leather Slip On Loafer Shoes 5.5SALOMON Contagrip Women's Shoes SZ 5.5 Eur 36.5 Black Suede Hiking Trail Slip On , SKECHERS WOMENS ULTRA FLEX -HIGH RISE /BLKAsics HN567 Onitsuka Tiger Womens US 9 Eu 40.5 Training Running Sneakers 83-4 , Women's ASICS Gel-Noosa Tri 8 Running Shoes Size 6.5ORIGINAL NEW BALANCE FOR WOMEN ( US SIZE 8 ) PRE-OWNEDLadies Skechers Vinyasa Flow Toe Post Thong Beach Fitness Flip Flops All Sizes , K - SWISS WOMEN'S SIZE 7 US BLACKPRE OWNED , Qupid SAVITA-01 Blue White Colorblock Knit Low-Top Platform Athleisure SneakerSkechers Women's Bobs Sport Photo Frame Charcoal 31362/CCL Memory Foam , Skechers Sport Women's Elite Class Memory Foam Fashion Sneaker Black Size 10 , New Adidas Womens BB2344 Black Pink White Running, Cross Training 8.5 6.5 nmdWomen's Klogs Women's Abilene Genuine Athletic Shoes , Women's Women's 9 Aetrex Black A Great Variety Of Goods Flats , Women's Creaciones D'Rossi Leather Loafters Reliable Quality Flats , adidas edge lux w Black - Womens - Size 10 B , Aerosoles Women's Midpoint Ankle Cuff Sandal Black Faux Leather Hook and LoopWomen's Shoes Bernie Mev Rigged Vivaldi Sneakers Black Metallic / Smoke *New* , Nike Women's Shoes Zoom Strike Size 8.5 US Running Sneakers AJ0188 016Asics Gel Excite 4 Women Running Shoe Size 7.5 Gray Purple Orange ,
"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."