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.Dailyshoes Women'S Classic Flats Memory Foam Cushioned Soft Daily Slip-On CasualLauren Ralph Lauren Gael Womens Shoes Flat Wedge Loafer Tassel Brown Ivory 9.5 B , Dansko Emmy Mary Jane misses suede shoes Size 38 7.5 - 8 lt greenNice~ JOSEF SEIBEL Brown Leather Slip-on Moccasin Comfort Loafer Women 7.5 M(38)Sperry Top-Sider Firefish Core Women's Linen Oat Boat Shoe 7MTrès belle paire de baskets HOGAN sneakers en daim, à saisirCroft & Barrow Black Mule Shoes with Buckle & Strap Clogs Size 7 Med A1901-6 , J CREW Cece suede Ballet Flats shoes sz 9.5 blue , Marc Joseph New York Manhasset Women's FLATS Floral GrissZara Women size 6 Three Tone Flats Shoes Pink Blue NWT Colorblock , OluKai Womens Kamiki Athletic Breathable Cushioned Running Water Shoes Size 8 , Easy Street Womens Barbara Low Top Slip On Fashion, Beige Floral, Size 7.0 vQSFWomens NIKE shoes Size 8 Womens Size 8 Tennis Shoes , SALON Shoes 783455 Yellow 36 , Women's Skechers Bob's Cozy High Slip-on Shoe Black Size 6 #NG2QK-104 , BROOKS Glycerin 14 Womens Red/Gray Athletic Sneaker Shoes Sz 7 , [EXO] The ElyXiOn dot Slippers KAI,CHANYEOL,SEHUN,D.O+Tracking No. , -Budweiser Bud Light Navy Clog Slippers Size LARGE 11/12 or SMALL 7/8Skechers Stolen Womens Ladies Outdoor Running Sport Athletic Comfort ShoesSkechers Womens - Gray Walking Shoes Size 9.5 (351848) , Reebok Crossfit Women's Nano Lime Green Purple DuraGrip Shoes size 8.5 , Skechers Go Walk Dazzle GOwalk Mesh Memory Foam Slip-On Shoes 7.5 M Light Grey +Puma Rebel Mid TT Mesh - Grey - WomensWomens Mizuno Wave Inspire 10 Running Athletic Sneakers Shoes 7.5 , Women's Authentic Nike LunarEpic Flyknit 2 Running Shoes Size 9.5 , Sketchers Mens Shoes Shape Ups 52004 Gray Training Walking Size 7.5 US , CONVERSE ALL STAR HI TOP BLACK SHINY SNEAKERS WOMENS SIZE 8 / MENS 7 /WOMEN'S REEBOK ZIGKICK TAHOE ROAD II RUNNING SHOES WHITE M42920 SIZE 8 WIDE , NIKE FREE TR FIT 5 RUNNING SNEAKERS (704674 100) WOMEN'S SIZE 7.5VANS Gilbert Crockett Pro Mid Demitasse Dachshund Classic MEN'S 6.5 WOMEN'S 8
"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."