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.Crocs Women Size 8 Slingback Slip on Ballet Flat Shoes Black Sh4Women's WHAT'S WHAT Black Leather Loafers Size 7M , Attilio Giusti Leombruni Link Women's Black Flat 38 EU/8 M US , New Women's Casual Flat Comfy Ballet Shoes Black candy3 , Michelle D Copper Brown & Black Mary Jane T-Strap Flats Size 7.5M , Indian Handmade Rajasthani Light Golden With Pink Thread Work Mirror juti WomenWomen's COLE HAAN COUNTRY Tan Animal Skin Slip On Loafer Sz 6-1/2B D10791 BRAZILDansko Sienna CORDOVAN US 9.5 Leather Stitched Heels Clogs Slip On EUC , Women's Cole Haan Slip On Mocs. Size 8 (B,M) Casual Multi Color Nubuck , Dansko Professional Clog Womens 40 Brown Leather Slip On Shoe Faux Wood HeelSperry Womens Boat Shoes Top Sider Brown Tan Size 6.5 Bluefish STS95287 61428 , Miu Miu Bow Flats Nude Size 35.5Liz & Co Women's Size 7 Brown Snake Skin Print Tassel Loafers Flats Shoes , Clarks Narrative Genette Harper Women Round Toe Leather Loafer Blue Zize 9.5MDemonia Black Vegan Buckle Zipper 2" Platform Goth Mary Jane Shoes Punk 6-12AGL Attilio Giusti Leombruni Womens Black Leather Toe Cap Ballet Flats Size 36 MWomen Girl's Lolita Round Toe Mary Jane Bowknot ballet Flats Shoes Plus SizeTahari Womens Frankie Closed Toe Loafers, Black, Size 7.5 4ejh , New! Dr Scholl's Womens Freedom Wide Width Walking Shoes-Size 6W-Black W86 la , Nike Women's Hypervenom Phelon III FG 881542-058 Max Orange Cool Grey Size 12Skechers 49336 Bikers Curbed Women’s Size 8.5 Brown Leather Shoes F1-1026 , American Sporting Goods Corp Ryka Womens Sugar Plum/Lime Shock/White Dynamic 5.5 , Nike Women's Metcon 2 Cross Training Gym Shoe Size 11 NEW 821913 106 Multi Color , NIKE WMNS WOMEN'S ROSHERUN FLYKNIT 704927-700 GOLD LEAD LASER ORANGE SIZE: 10PUMA BASKET PLATFORM RESET WOMEN'S BLACK LEATHER SHOES SZ 9, $110. , Vasque Women's Trailbender II Size 8.5 US Ebony/Mint (VS18W-Misc) , Reebok Women's FREESTYLE HI METALLIC Shoes Feather Blue CN0959 bConverse Chuck Taylor All Star Animal Print Junior GIRLS , WOMEN’S GUESS SHOES WHITE LEATHER SOLE LOGO LINE SIZE 8.5Vans Authentic All Black Shoes Sneakers Trainers 6 3.5 36
"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."