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.Cross Trekkers Shoes Sz 11 Mary Jane Walking Loafer Sporty Athletic Brown WomenWomens Ladies Low Pearl Heel Slip on Flat Casual Smart Office Loafers Pump Shoes , Born Women's 6.5M Brown Leather Mary Jane 1" Wedge Shoes Boho ChicClarks Bendables Brown Suede/Leather Clogs Shoes Mules US sz 11m Women’s EUCRockport Women's Weave Woven Loafers Sz 7.5 M Brown Leather Casual Comfort Shoes , KLOGS *6.5 Med* Black Leather Basketweave Edge Design 2" Wedged Heel CLOGS ~ LNSTYLE&CO Style & Co. Womens Alisson Closed Toe Ballet Flats Black Size 9Naturalizer Clarissa Slip on Casual Shoe- Women's 7 M- CoffeebeanAetrex Brown Leather JULIA Mary Jane--Diabetic/Feet Issues--Size 8XWGUC Sam Edelman Farrow Ballet Flats Burgundy Satin Material 6.5 M , Tods brown suede penny loafer flats. size 6.5 , AGL Attilio Giusti Leombruni Womens Black Leather Toe Cap Ballet Flats Size 39 M , NWOB House of Harlow Kye Studded Leopard Calf Hair Leather Slippers, Size 37.5 , Women's Skechers Gray Flat Working Shoes Sneaker US7 UK4 EUR37 , NIKE AIR MAX Womens 8.5 Running Shoe Black Graphite Magenta *EUC* Worn Twice!Anne Klein Womens Ursala Cap Toe Ballet Flats Black Size 6.0 u3g1Women Casual Solid Soft Leather Pointy Toe Moccasins Flat Heel Shoes Plus Size , Womens Leather Oxfords Rivets Punk Flats Heel Slipper Mules Loafer Shoes Fashion , VANS Off The Wall TB4R Classic High Top Neon Green Skate Shoes Sz: 5.5Mn's-7Wn'sMens GENUINE LEATHER SLIPPERS BROWN COLOR HQ , Tony Little Cheeks Purple Mesh Easy Shapers Fit Body Trainer Sneakers 8 SALEMerrell Women’s Gore-Tex Continuum Trail Hiking Shoes Gray Near Mint! Sz 7/37.5 , Nike Wmns Air Force 1 One AF1 Flyknit Mid Black White 818018-002 7.5Asics GT-2000 Women's Gel Guidance Line Multi Color Running Shoe Sz 6 8991NEW Vans Patent Leather SLIP ON Shiny BLUE Iridescent Womens 5.5 MENS 4 Shoes , SKECHERS USA Inc 22846-TPE Skechers EZ Flex 3.0 Aroundtown Womens Slip On , PUMA X RIHANNA WOMENS FENTY SURF SLIDE (Dazzling Blue-Evening Blue ) 367747-03 , New new Balance model wxnrg women walking sneakers size 8 color black , NWT LACOSTE Women's Ziane Leather Sneakers size US 10 , New Balance Womens Ww928ws3 White/White Walking Shoes Size 10.5 (3E) (351864) ,
"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."