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.Jorge Bischoff Womens 8 Black/White Patent Gold Accent, Suede Strip Ballet Flats , Vince Camuto Womens Pointed Toe Flats Shoes 8 , Emporio Naka Sao Paulo Womens Mary Jane Shoes Black Leather Size 6.5 - 7 / 37$89 Sperry Angelfish One Eye Boat Women's US 7 in Linen/Oat Leather , Selby Ladies Loafer 8.5 Mule Black Slip-On Soft Leather Active Flex Brazil , Womens 5 B M Cole Haan Air Bria Beau brown leather tan linen mule shoes slip-onDansko Women's Black Leather Slip On Clog Nursing Pro Work A04 Size 40 US 9.5 10Keen Womens 10 Mary Janes purple/pinkSOLESENSABILITY WOMENS SHOES CASUAL UTILITY FLAT METALIC SIZE 7 , LADIES SPOT ON MESH BALLERINA SHOE AVAILABLE IN BLACK & CAMEL STYLE - F80142Ladies Vtg Authentic Isaac Mizrahi Dark Brown Velvet Ballet Flats Size 10B Italy , Too Fast Blue Sailor Ankle Strap Flats Women's Shoes Size US 10 , Merrell Ceylon Monument Red Mary Jane Shoes Gray Womens 7 , Aldo Women’s Ballet Flats Size Euro 37 US 6.5 Leather Off-white , L.A. GEAR STREET HIKEING SHOES SIZE 7 1/2 CANYON CRUISER LOW STYLE 6315 BLK NIBNEW BY A. WOMENS BALLET FLATS , SAS 8.5 M Beige Leather Mary Jane Moccasins Tripad Comfort Shoes Made USA $168 , Vans Women's Classic Low Sneakers Skate Tennis Shoes Grey Size 8.5 New 721356 , Skechers Womens 22459 BlackSuede/Mesh/CharcoalTrim Walking Shoes Size 9.5Women's Skola Leah Clog, Mahogany, 41 Characteristical FlatsADIDAS V JOG K SHOE SHOES SPORTS GIRL GREY/ROSA BC0083 (PVP IN STORE 49E)Puma x Fenty by Rihanna Trainer Mid - Black - Womens , S-7 Saucony Guide 7 Women's Running Shoes, Size 5M US , OG WOMEN NIKE OCEANIA QS RUN WHITE ORANGE KHAKI RACER RUNNING SZ 7.5 T BROWN , Asics Womens Rhythmic 2 Studio Training Dance Shoes Size 12M Pink/Black (S385N)Asics Gel Cumulus 20 Black/White Running Shoes Women's US 7.5 (P2,17) , New Balance Womens Ww847gr2 Grey Walking Shoes Size 9 (C,D,W) (357226)NWOT Clarks Outdoor Muckers Womens Hiking Walking Shoes Black Nubuck Sz 7.5 WNike Wmns Flex Experience Run 4 Wome's Running Shoes 749177 012 Grey SZ 8 , Keds Champion Oxford Black/Black Canvas Women's Sneaker WF24700
"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."