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.Spot On F8631 Ladies Textile Dolly ShoesCharles Albert Women's Coral Cobra Pat Flat 8M , comfortview shoes women Mules Slip OnsWomens Flat Suede Kitten Cat Stitch Walking Ballerina Pump Shoes Ladies US 5-10 , ANN TAYLOR Women Ballet Flats Size 6 M Black SuedeNWOB Sesto Meucci Blue Sheen Fabric Slip-On Loafer Shoes Pumps WOMEN'S Size 7 , Ecco Light MaryJane Womens 38 US 7-7.5 Strap Buckle Flats Shock Point Brown , NEW $139 VANELI designer women shoes Flats Moccasin Oxford Comfort 7.5Pieces Kate Women's Red Heart Round Toe Suede Ballerina Pumps With Bow New , Adult Women 5 1/4" Wedge Pf Monk Creeper Skull Buckles Side Zip Shoes Flats , Via Spiga Women Shoes Size 9 New Slip On , EUC **NINE WEST** Vtg. American Collection Blk. Leather 4" Heel,Clog, 8M, Euro39New Women's Skechers Bobs 34371 Sportlights Slip Ons Size 7.5 - Natural (L15)Nike Free 5.0 Ice Cube Blue/White Running Sz 9 Women 642199 402 , Joie Huxley Slip On Sneakers Camouflage Us 6 MSRP $235 NewWomen's Brooks Adrenaline GTS 15 Running Shoes size 6 Narrow 2AWomen's Chocolate Brown Suede Dress Shoe EUC, Size 6 , Skechers Street Double Up Shiny Dancer Sneaker Women's SZ 10.0 M Silver D8062Vans Sk8-Hi Unisex Imperial Purple/True White Skate Shoes Men's 4.5/Women's 6M , Under Armour Womens Sz 6.5 Waterproof Water Sneakers Shoes Running Walking GrayWomen's Montrail Rogue Racer Women's 7 Complete In Specifications Athletic ShoesWomen's Holster Beachside Jelly Wedge Shop Flats , Nike Air Huarache Run Black/Black-White 634835-006 Women's SZ 6.5 , Nike Maryjanes Walking Comfort Shoes Women Size 8 Great Condition , PONY SHOOTER '78 HIGH CHEVRON SNEAKERS WOMEN SHOES MIX 1781 SIZE 8 NEWNike Dunk Low Covnac/ Sanddrift Sienna Sheen 309324-212 Women Size 8 , Brand New Calvin Klein SIGNATURE CK Logo Flats Slipon SNEAKER SHOES 6 White , New Balance Womens 590 Running Shoes-Women's Size 8M Grey/Pink , CONVERSE ALLSTAR Light Gold/Ligh Hi Top RUBBER Sz 7 Women'sSPERRY Top Sider Pier View Sneakers Shoes color Navy Cobalt Print Size 8.5M NEW
"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."