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.Cole Haan Women’s Metallic Bria Grand Leather Sneaker Size 9.5M , Brighton Black Brown Croco Leather Silver Buckle Shoes Size 7.5Women's Clarks Black Leather Mules, size 8.5 , Womens Loafers Slip On Shoes Sz 8 Wide Weave Casual E Collection Fashion , Naturalizer Womens Size 7 1/2N Shoes Black Leather Mules Slip On 140N77 , J Crew Black Suede Round Toe Elastic Ballet Flats Size 7 , EMU Australia Springvale flats size 10 , Cole Haan GRAND.OS Women US Size 6 Green Patent Leather Boat Shoes Driving Moc , Steve Madden Exsess Loafers Pewter Metallic Women's Slip On Shoes Size 8.5B , AVON! Cushion Walk Genuine Suede Jeweled Flats. Sz6.BLACK Shoes. Women/Jrs! NEW , $200 VIA SPIGA DOTTIE Dark Olive Green Snake Leather Designer Ballet Flats 9.5 , LADIES SHOES/FOOTWEAR - Neckermann Thong N2602 white floralBass Womens Leather 1.5" Heeled Penny Loafer Slip-On Shoe Reddish Size 6 M , Nike Women's Tailwinds 6 Athletic Running Shoes Size 9 , Women's Saucony Excursion TR8 running shoes sneakers size 7.5Lands End Womens Sz 9 Water Shoes Mary Janes White Gray Purple Mesh$250 SKECHERS Women BLACK CHILL FLEX MEMORY FOAM SLIP ON SNEAKERS SHOES SIZE 8 , Vintage REEBOK CLASSIC Women's Size 8.5 White Leather Navy Blue Athletic ShoesWomen's Ladies Rieker Trainers 59570 Crazy Price Athletic Shoes , Women's Dansko Richelle Clogs-Women's 7.5-8 Black Crazy Price, Birmingham FlatsWomen's Sperry Nahla Sand Woven 10M Serviceable FlatsReebok Womens DMX Lite Outdoor Shoe- Pick SZ/Color.Teva Women's Ridge Peak Hiking Shoe - Size 7 - Desert Taupe , UNDER ARMOUR W MICRO G LIMITLESS TR WOMEN'S GREY/RED SHOES , New Balance 530 Ceremonial Women's Running Shoes W530CEB NIB Authentic , Vans Iso 1.5 Mesh Knockout Pink Women's Size: 9Merrell Womens Aqua Bare Access Arc 2 Running Shoes Sz 8.5 US Vibram J58082 BluePuma Basket Mid WTR Puma White 361156 03 Women's SZ 8 , New Balance Women's T510v3 Trail RunnerCONVERSE,Chuck Taylor's,Women's 10, FUCHSIA GLOW FLORAL HI-TOPS,tennis shoes,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."