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.Talbots brown snake embossed leather studded ballet flats sz 6.5 , Womens Andiamo Marissa Peep Toe Slingback Pump Black -7M , 424 Fifth Womens Gigi Black Leather Loafer Mule Shoes 7.5 Medium (B,M) BHFO 15469 M Right Lift 1/2" Kiltie Tie SAS Loafers Leather WOMENS SHOES Oxford Casual , MERRELL Sz 10 Forecast Torch Moc Dark Brown Suede Waterproof Loafers Shoes -Ai12 , White Mountain Cliffs Navy Blue Baseline Maryjane Shoes 6.5 NEWVionic Spark Kiska Round Toe Flats - Natural Snake , Klogs Missy Women's Clog Shoes Display Model Apple Blossom 8 M , SAUCONY EXCURSION TR6 RUNNING WOMENS 10 SHOES , Tahari Klinton Mules - Women's Size 10M - BlackSalvatore Ferragamo Aladina Size 7.5 AA Brown Leather Women's Loafers EUC , Skechers Goldie - Diamond Darling Pewter Womens Fashion Sneaker Size 7MRocket Dog Women's Jamaica 8A Canvas / Solar Power PU Sneaker, Sz 9.5, DefectL.B. Evans Mens Klondike Slipper,Saddle Size 9 NEW In BOX , Women’s AIRWALK Canvas Sneaker Multi Pink Green Striped Tennis Shoes Sz 9 NWTNB NEW BALANCE WALKING SNEAKERS SHOES WOMENS SIZE 8 2A NARROW LKNEWSKECHERS Shape-ups fitness athletic sneakers gray leather & textile size 9 , Womens Nike Presto Fly Black White Size 7 , KEDS Classic Womens Slip On Flats Navy Blue Comfort Shoes size 8.5 NICE" , Skechers Equalizer Cross Training/Running Shoes Women's Size 8.5 11890 CCLB EUCSTEVEN by Steve Madden Hilda Slip On Fashion Sneakers 608, Black, 7 US , NEW BALANCE WOMENS 580 ELITE EDITION CORAL SORBET SHOES SIZE 7.5 WRT580IK , Womens Skechers Shape Ups Black White Tennis Shoes Sneakers Walking Size 8 , Vans SK8 HI SLIM ZIP Leather Wind Chime/Blanc De Blanc Men's 4 Women's 5.5Skechers Womens Flex Appeal 2.0 Bold Move Fabric Low Top, Black-white, Size 7.5 , Madden Girl Starstrk Faux Leather Platform Sneakers, Women's Size 6, White , Saucony Peregrine 4.0 Womens Running Walking Athletic Trail Shoes US 7 Euro 38 , Sanuk Womens Toe The Line Natural Ikat Shoes Sandals Canvas Shoes US 11 NEW!Women's Size 9.5 M Bass Yukon Green Suede Leather Hiking Trail Shoes Boots , SAUCONY KILKENNY XC ORANGE / RED TRACK & FIELD SPIKE CLEATS WOMEN SIZE 10 ,
"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."