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.Steve Madden Womens P-Helena Woven Ballet Flat Shoes, Fuchsia, US 7 , Bolaro WOmen's Jeweled Casual Dress Round Toe Flats Blue Size 6MBlack Sparkly SPERRY TOP SIDER Loafers with BowDr Zen Chris Women's Therapeutic Casual Extra Depth Shoe Size 9 New No BoxCute Adorable Stylish Peach Ellie Shoes 1" Oxford Flats Adult Women , SANUK FOLKLORE BLACK MULTI SIDEWALK SURFER SHOES, SIZE US 7/ ~NWTEarth Origins Natalie Ballet Flats Women Size 7.5 Brown Leather Embroidered ShoeSoft Spots Shoes Leather Size 9 M Womens Taupe Slip On All Day Comfort Walking , Ballerines SAN MARINA Daim Noir T 36 TBE , PAUL GREEN Brown Leather Slip On Dress Loafers Shoes Size 5.5 , BALLERINES SOIR DE LUNE MOD.MADRID NEUVES!!!!US Indian Punjabi Jutti Bridal Shoes Khussa Shoes Mojari BEADED SANDALS SS163 , TORY BURCH Tan W/ White Trim Leather Bow Ballet Flats Women's Size 7.5 M Cute! , Birkenstock Footprints Women’s Eur 36 Slip On Shoes Brown Leather Loafer MuleTEVA Hydro Life Ballerina Slip On Shoes Coral NEW Women's Size 10 Water ShoesAvenger Women's Ladies A7150 EH Oxford Composite Toe Work Shoes M W NEW IN BOX , Asics Gel-Exert Tr Shoes Women's Cross Training Running Walking Grey .Sz 9 M , LA Sportiva Trail Running Shoes Womens Size 7 , Women's Converse women sneakers 6/boys 4 Unusual Athletic Shoes , Women's Skechers Womens Toners style Low-priced Athletic Shoes , Women's Ballerines SEE BY CHLOE t.36 Exquisite FlatsPaperplanes Womens Fashion Casual Leather High Top Sneakers Shoes 1338 CA , Merrell Around Town Sunvue Slide Women's Size 7 Black 25%OFFWmns Nike Air Max Jewell WQS Barely Orange Women Running Shoes NSW 919485-800VANS Sk8 Hi Slim African Violet/True White Casual WOMEN'S SIZE 9Womens Converse Burgundy Chuck Taylor All Star Ox Low Top 139794F NEWAdidas Women's Pure Boost X Running Shoes Size 10.5 AQ3399 Ray Red/ White , Inov-8 Bare-XF 210 Unisex Cross-Training Shoe Black/Grey/White 3.5 W UK , Women's Asics Gel Contend 2 Purple & Dark Gray Running Sneaker (8) , Reebok Women's Speedlux 2.0 Running Sneaker CN1490 ,
"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."