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.Sam Edelman Krissy Women's Espadrille Flat SZ 6MWomens Ladies Girls Flat Geek T Bar Cut Out Office School Work Pumps Shoes Size , STUART WEITZMAN Women's Black Pumps Block Heel Square Toe Suede Velvet 8 M , Women's Size 9 Elaine Turner Gold Buckle Chain FlatsSesto Meucci women's shoes/slides size 7NCloudwalkers Womens US 13W "Carol" Silver Bow Peep Toe Ankle Strap Flat WedgeUNION BAY CAMEL WOMENS BEIGE SOFT COMFY LOAFER SLIP ON FLAT SHOES SIZE 9.5 MWomen Flat Loafers Round Toe Slip on Multi-color Summer Casual Lazy Boat Shoes , Sperry Top-sider for J.Crew Blue White Pink Canvas Striped Deck Boat Shoe Sz 6.5Annie Shoes Eastly Faux Leather Ballet Flats, Women's Size 9M, Black/SilverNEW Women's Soft Spots Constance Bone Leather Slip on Comfortable Casual ShoesLUCKY BRAND Abelle 2 Black Suede Driving Moccasins Loafers Shoes Size 7.5 EUC , BANANA REPUBLIC ARIELLE KILTIE FLATS in NEW VERMILLION , Chocolat Blu Costa Flat Graphite Women's ShoesWolky Womens Mary Jane Wedge Shoes Black Suede Leather Sz 39 US 8 Buckle Comfort , SIZE 9 Women's Black & Floral Athletic Sneakers Comfortable High Heel Shoes , Womens Get Fit Yoga Walking Running Sports Gym Lightweight Mesh Trainers , Nike Shox Shoes 311233 118 SZ 9.5 Orange White 050709 LN3Pink Gladiator Handmade Knitted Rope Women's Sandals - Sizes 4-10 US WNaturalizer Womens Fearn Fabric Closed Toe Mary Jane Flats Blue Size 11.0 1aTv , MENS HOLIDAY ELF SLIPPERS JINGLE BELLS CURLED TOE POM POM LARGE 11-12 NEW , Womenss Saucony Cohesion 10 Gray Running Shoes Size 9M (Z875)Women's Giuseppe Zannotti Flats 37.5 Various Styles Flats , Skechers 22857 Sport Womens Fiery Fashion Sneaker- Choose SZ/Color. , Nike Air Max 90 FB Black White Leopard Boys Size 6.5 Womens Size 8 Running KidsNEW BALANCE - Women's 10 D Wide - WX857AB2 Cross Training Shoe - Black Leather , WOMEN'S ADIDAS DURAMO 8 W CP8754 ATHLETIC RUNNING COURSE A PIED SHOES SIZE 9 , Merrell Women's Black Circuit MJ Breeze-1 Outdoor Mary Jane Mesh Size 9.5NIKE Training Zoom Fit Women Running Shoes Size 8 Fuchsia Pink 704658-602 ,
"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."