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.WOMENS LADIES LOW HEEL OVER KNEE HIGH CONCEALED WEDGE RIDING BOOTS SHOES SIZEDR SCHOLL'S Women's Black Slip on Size 8 W "VERMONT" , JIBS Suede Rubber Soles Slip-On Winter Snow Drawstring Clogs Mules Women's US 8 , Clarlk's women's shoes.Black . 8 1/2.LADIES ARIAT BROWN LEATHER TASSLE MULE CLOG MENDOCINO STYLE 93897 SIZE 6 BMERRELL Women's Moccasin Loafer Flat Slip On Shoes Beige Mesh Size 8 , Zee Alexis Womens Gordie Shoes Black 9 MPale Red El Naturalista Flats with Diagonal Strap 6.5 37 , CHACO Outcross Evo Mary Jane Hiking Water Shoe Sandal Black Gray Women’s 7 (A08)Skechers Sport Ultra Flex Capsule Women’s Size 7.5 Pink Sneaker Shoes TX-15Women Running Brand Shoes Female Sports Shoes non-slip Outdoor Walking ShoesIlse Jacobsen Tulip Shoes Maroon Wine Slip On Comfort Flats Size 40 / US 8Women's Merrell Avian Light Ventilator J89466 Sz 6.5Brooks Glycerin DNA Women's Running Sneakers Size 9.5 Shoes Pink 1201371B813 , Nike Flex Supreme TR 6 Sneaker - Women's Size 7.5 Gray DAMAGEDDansko Fashion Sneakers Burgundy Leather Women36Medium (B, M) , Steve Madden Women's Breeze Ankle-High Fashion Sneaker , Skechers Women's GO STEP Wild Walking ShoeBlackUS 5 MSuperga 2750 Cotu Classic 2 - Choose SZ/Color , Dolce Vita Women's Tina Sneaker - Choose SZ/Color , Pacific Trail Klamath Sandals Women's Shoes , New Balance Women's Vazee Rush v2 Protect Pack Shoes Black with Silver , Women Reebok AR2645 Classic leather ripple Casual shoes white blue red sneakers , New Balance Women's 696 Shoes Blue with White , Roxy Bayshore III Shoe - Heather Grey - NewSkechers Sport Women's Breathe Easy Serendipty Fashion SneakerBlack8.5 M USNew Nike Oceania Nm Womens Sports/Casual ShoesNew Balance Womens Trail Running Sneakers 510v3 Size 7 Med Shoes , 14927 Navy Skechers shoe Go Walk 4 Women Soft Casual Slip On Walking Loafer Mesh"Mizuno Women's Wave Inspire Running Shoe,White,2A, AA Narrow ,
"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."