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.Cole Haan Women's Olive Green "Country-Style" Suede Moccasins Loafers - size 6BSperry Jersey Gray Jersey Sequin Top Sider’s Women’s Size 9 , Worthington Sport Size 5 Women's Beige Leather Loafers Jl062917 , Dexflex Comfort Black Women’s 7.5 Patent Toe Wedges Slip On Shoes , Michael Antonio Darn PU Sneakers Women's SZ 5.5 M Black NEW DISPLAY D6062Yosi Samra Sandrine Womens Sz 7 Ballet Flats Foldable Packable Striped NeutralAerosoles Brown Buckle Suede Loafers Moccasins Ballet Flats Women's Size 6.5 M**Calvin Klein Celia Loafer - Women's Size 8, Black , EMU Ridge Australia BROWN Suede Shearling Lined Moccasin Slippers Men's Sz 13 , Cole Haan Womens Black Sneakers Size 9Nike 317061 151 Women's Air Stab White Blue Pink Athletic Running Shoes Sz 8.5Oboz Footwear Women's Sawtooth Low B-Dry Hiking Shoes Violet/Purple Sizes 9.5 , NIB Reebok Women Classic Aerobics Desire II Hi-Top Fitness White Gray Shoes 7.5Women's New Balance 680 v3 Running Shoes Size 8.5 US , LADIES K-SWISS COMFORT TRAINERS, WHITE AND PINKBrooks Defyance 3 White Blue Running Shoes 8.5 Eight 1/2 Women's 42.5 EuropeanWomen's Women’s Ballet Flats Size 7.5 Clearance Price FlatsNEW NIKE FREE 4.0 PRINT Black Bright Citrus WOMENS 729515 001 NIB , Nike Women's Ashin Modern Run Summit White/Crimson Tint Size 8 , NIKE IN-SEASON TR 7 WOMEN'S BLACK TRAINING SHOES, SIZE 8 NEWNike Free TR 6 Metallic Silver Black Green Glow Special Edition New Women Trail , adidas barricade club - Black - Womens , Skechers BOBS Womens Bobs Cloudy-Rainbow Fashion Sneaker- Select SZ/Color. , Under Armour Women's Threadborne Slingflex Running Shoes 1285490-001 Black/Grey , WMNS NIKE Zoom Hyperquickness TB (599515-600) SZ 13.5 CM: 30.5New Womens Dark Gray Adidas Galaxy 3 Tennis Shoes, Size 8 , COLUMBIA RAVENOUS STABILITY II WOMEN'S TRAIL SHOES SZ. 9.5, 10 ,#BL3757-060 , Converse Sz W 13 M 11 Men All-Star Ox Silver Glitter Lo Top Sneakers , ASICS Gel-Contend 3 Womens Indigo/Aqua/Pin Sneakers , NEW COLE HAAN WOMENS WOMEN'S GRAND CROSSCOURT HIGH TOP SNEAKER - STORMCLOUD S... ,
"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."