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.HOT CAKES SHOES WOMENS SIZE 11 W MISTY , Style & Co. Womens Ciaraa Closed Toe Ballet Flats , Nine West Animal Print Flats Size 9.5Dr. Scholl's Scout Women's Loafers SZ 6MBallet Pumps, Leather pink leopard Teenage flat ballerina ,Anniel shoes ItalySperry Top-Sider Angelfish 9102047 Tan Leather Boat Shoes Womens Flats Sz 9.5 MDr Scholls Joliet Black / Grey Striped Slip On Flats Shoes Sz 7M excellentJosef Siebel Moc Toe Loafer Slip On US 9 Leather Black Women Hungary , Skechers Dreamstep Enliven Casual Slip On Shoes - Women's Size 11 - Black , ARIZONA HEAT LADIES CLARKS LEATHER SLIP ON BALLERINA BOW FLAT CASUAL PUMP SHOESZARA SHINY HEELED LEOPARD PRINT COURT SHOES MEDIUM HEEL SIZE US 9 , Naturalizer Natural Soul Fareeda Driving Moc Loafers Slip On Shoes Women's 9.5Biala 9 Gray Slip On Shoe Women's , New Womens Casual Gym Walking Loafer Slip on Sport Flats Tennis Athletic ShoesWomen's New Balance Flex Ride Running Shoe Grey/Lime 10.5WARCOPEDICO Women’s Beige Sec Stretch Knit Shoes size 41 US 9.5 10 Washable! , Vans Hello Kitty Hi Top Sneakers Hi Top Sneakers Bows Black Size Women's Sz 8.5 , Women's Converse Size 6 Vanilla Off WhiteWomen's Sneakers Flats Athletic Mesh Breathable Platform Sport Casual Shoes NewWomen's Nike Zoom Courtlite 3 Platinum White Black Blue Tennis 487996-001 sz 9.5 , Converse One Star Pink Purple Womens Sz 9.5 Shoes Sneakers Wild Bright Colorful , Nike Air Max Torch 4 Running Shoes 343851-061 White / Pink Women's US 6Nike Womens Size 10 Flex 2017 RN Gray Athletic Running Training Shoes F3-145Women's NEW BALANCE Sneakers (Size: 7) Outstanding Features Athletic ShoesWomen's tory burch espadrille 8 Attractive Design FlatsNew Balance WID626v2 Work Shoes-Women's size 8 D Black , ASICS GEL-Sonoma 3 Running Shoes-Women's size 9 Black/Mint , ASICS Gel Domain Volleyball Shoes Women’s Size 8.5 US Near Mint ConditionVibram Women's Fivefinger Komodo SPORT Velcro Running Shoes W3664 Size 37 , CONVERSE All Star Chuck Taylor Black High Sneakers Womens Size 5.5 High Rise
"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."