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.$59 Steve Madden Womens Surphur Flip Flop Toe Post Sandal Flat Shoe, Green, US 6Skechers Womens Shoes Leather Size 8.5 Oxfords Zipper Side Pocket Brown , Bearpaw Womens haven Suede Closed Toe Oxfords, Slate Blue, Size 6.0New York Company Women's Ballet Flats Shoes Black Size 6MSpot On F8754 Ladies Black Synthetic Suede Dolly Shoes , WOMENS DANSKO Professional Stapled White Leather SHOES CLOGS 40 , Corky's "Zigzag" brown & Off white slip ons - Flats womens size 9 CorkysHOLSTER FASHION WOMEN'S SHOES Bronze Explore Sneakers Size 39WOMENS BEACON COMFORT WELL White 2 STRAP SHOES SZ 7WW , Merrell Jungle Slip Ons- Women's size 8 Black (Damage)DEMONIA CRE108/RPT Women's Punk Goth Red Platform Studded Heart Creepers Shoes , Cole Haan Womens Mikaelasam Closed Toe Loafers, Purple, Size 6.0 , Women's Athletic Shoes Outdoor Running Casual Sports Breathable Sneakers WalkingSkechers Street Women's Women's Side Street-Core-Set SneakerComfort Maven Bette Casual Flat ShoeAdidas Neo Women Size 8 CF Advantage CL CloudFoam White Shoes Sneakers***NEW*** Bensimon Ballerina Shoes Canvas Color Nude U.S. Size 6 euro 37Abeo Athletic Running Shoes Women's Sz 9M White Orange Synthetic (tu36)BLOW OUT SALE @ CONVERSE All Star Shiny Wedges Cream Athletic Shoes Size 9 ??b3Nike Roshe Run Cool Gray Womens Size 9 , BROOKS ADDICTION 10 Running Shoes Women's Size 5New Balance WCOASCP2 B Black Purple Women Running Sheos Slip-On WCOASCP2BPuma Basket Heart DE Women size 9 Color: Blue/White , Zoot Women's Laguna Running Shoe, Pacific/Mist/Aqua, Size 6.5NEW ADIDAS VIBE ENERGY BOOST AWESOME WOMEN SNEAKERS SHOES SIZE 7 7.5 8.5 B23002ASICS GT-2000 T2K7N Women Purple Pink Athletic Running Sneakers Shoes 8.5 M , Hoka One One Conquest Womens size 8 Running walking training ShoesBrooks Ghost 8 Running Shoes Womens Size 9.5 Charcoal Bright Rose Bluebird F7 , Columbia Graci 2 White Leather Slip On Walking Shoes Womens 8 Med Sneakers Blue , Rocket Dog Womens Jolissa Aviator Canvas Fashion Sneaker, Black, 8.5 M US
"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."