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.Rieker Antistress Closed Toe Open Backed Brown Shoes SizeWomen's Merrell Oceania Sand and Brown Leather Flats Shoes US 8.65MERRELL MOC AIR Cushion Clogs Hikers Comfort WEAVE MULES SHOES WOMENS SIZE 6 , Dolce Vita Ollie White Leather Pointy Cap Toe Loafers Women’s Size 8.5 M*Cole Haan Metallic Brown Leather Patent Leather Flat Shoe Size 8.5 , CLASSIC ELEMENTS WHITE SHOES WOMENS SIZE 6 1/2 M ELTONHunter Womens Original Canvas Plimsoll Desert Camo Pink Slip On Size 8 New , Andre Assous Shelley Gold Womens Shoes Size 6 M Fashion Sneakers MSRP $17502-2569 Soft Style Fairfax (Gunmetal Vitello Women SIZE 8.5 EWASICS Gel Cumulus 16 Womens Running Shoes 7.5 Sneakers T489N Blue Green , New Balance 409 Cross Trainer Shoe Womens - Sz 7.5 White/Silver/BlueNine West Mortez Women's Fashion Sneakers Grey Multi Size 7.5M , Ted Baker Men's Nnyah Slipper Sz.42Puma Flare Graphic - White - Womens , VANS OFF THE WALL Cherry Red Skate Loafers Athletic Shoes Womens Size 7 ?b8Skechers 22043 Womens 9 Med Cream Beige Mule Clog Slip On Sneakers Shoes LeatherUnder Armour Cartilage Sz 8 Women Silver Blue Running Shoes EUC YGI A8 , GUESS WOMEN'S BROWN MULTI TENNIS SHOES SIZE 8-1/2" WGANABETH2 NWT FREE SHIPPINGWomen's Born Toby Black 6.5 New Varieties Are Introduced One After Another FlatsWomen's Black Flats Size 6 Shop Flats , Adidas Originals ZX TUBULAR RUNNER WHITE SHOES Superstar Womens B25087 US 11NIKE WMN BLAZER MID SUEDE VINTAGE SIZE: 5.5 FASHION NEW RARE RETAILS FOR $100! , Zee Alexis Womens Kerrigan High Top Sneakers Olive 9.5 MNew Balance Women's W420v3 Running Shoe Pomegranate/Outer Space..Size 9.5 B , New Balance 88V1 Blue / Black / Pink US Size 11 - FREE SHIPPING - BRAND NEWWomen's SKECHERS Gratis - Light Heart-slip on gray sizes NIB comfy!!! , NWT CoSTUME NATIONAL Women's Silver Glitter Oxfords l6S5A2980739 Size 41 (11) , Skechers Women's Endeavor-Venturer Taupe Fashion Sneaker - Size 7 / 8Women's Skechers Empire - Inside Look - Black/Multi - New!!! , Reebok Women BD5209 Aqua Grip TR Swim shoes blue grey white Sneakers ,
"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."