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.Women's Alpargata Huarache MADE IN MEXICO , EXPORE 24 Easy Spirit SHOES WOMENS SIZE 7 1/2 M , Women's, Maui Island Boat Shoes, Jiffy, US 8.5M , Comfortable White Dove Woman's Size 8 Beige Ballet Flats , NEW SPERRY TOP-SIDER Canvas GREEN BOAT SHOES WOMENS 8.5 , Womens Mephisto Air Relax Brown Leather Mobils Tstrap Flats Euro 37 US Size 6.5 , DANI BLACK SNAKESKIN PRINT LOAFER SIZE 7.5M , Ladies Sonita Professional Black Leather Slip On Wedge Clogs Sz 37 6.5 - 7 fw218 , Vintage Womens Woodbridge Red White Flats Loafer Shoes Sz 8.5 Summer Fun Workwomens 10 10.5 41 ECCO BIOM Lite soft black leather walking shoes sneaker oxford , Dr. Scholl's Women's Leather Tassel Loafers pale green size 10 W, comfortable , Sesto Meucci Women's Slip on Loafer Sz 6.5M Black Leather Front Zipper Euc , Ladies Skechers Go Walk Hot Pink Slip On Casual Shoes Style 13510Ballet Flats Crochet Hippie Chic Painted Bird Blue Bird Ankle Flats 7 $74 MINTSkechers Go Walk Lite Daisy Gray Womens Slip-On Size 11MReebok Zigsonic Running Shoes, #V51083, Wht/Grey/Lime/Blue, Women's US Size 9 , Women's Light Running Athletic Shoes Breathable Outdoor Walking Casual Sneakers , Skechers 47844 Women's Brown Leather Casual Shoes Size 9 S269ASICS Gel Surge Women Running Shoes Size 6.5 White Purple T18CK , Puma Womens Fierce evoKNIT Gray Fashion Sneakers 9.5 Medium (B,M) BHFO 5428NIB Authentic $150 ORIGINAL ADIDAS STAN SMITH Snake Embossed Leather Shoes Sz 9M , [CM8903] Womens Reebok Classics Freestyle F/S HI Satin Bow Sneaker - WhiteMerrell Womens SHOES SIZE 9 MERRELLS 9 MERRELL HIKING SHOES 9 , White Mountain Women's Carly Denim Blue Suede , Nike Womens Running Shoes Size 8.5 (16766)Skechers Women's Go Walk Outdoors-runyon Sport SandalConverse CT AS 2 Ox Sheen Mesh Indigo Women's Low Top Trainers , VANS Era Black Classic Gum Skate Shoes MEN'S 6.5 WOMEN'S 8Puma Suede Classic - Blue - WomensBaskets Femme samples shoes ETNIES BRIGADE TAN GUM WOMEN
"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."