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.Clarks Artisan Style 74530 Brown Stitched Wedge Mule Clogs Women's Size 10 M , Women's Nurture Leather Slip On's Sz 8 Black Shoes Comfort Sole Career Work 144 , Women's DIESEL FOOTWEAR ODESSA MARY JANES Slip On Shoes Beige Leather Size 8.5 , STEVE MADDEN Benzz Silver Peep Toe Low Wedge Heel Pumps Shoes Size 6.5 , Low Heel Round Toe Tassel Woman Shoes Oxfords Martin Womens Shoes England retroAthena Alexander Womens Taffy Closed Toe Ballet Flats Blushed Size 6.0 6COgSoft Style by Hush Puppies Women's Valda Oxford, Black Snake, 8.5 M USBorn Concepts b.o.c Size 9 Slip On Clogs Shoes Beige Comfort Nurses , Cliffs by white mountain women's shoes felice ballet flat black size 6.5 , Rock & Republic Ballet Flats Blue & Black Women’s Size 8.5 MRALPH LAUREN Collection Size 6.5 Brown Leather Penny Loafers Flats Shoes 6 1/2Aerosoles Women's Upper Level Flat, Black Combo, 7.5 W USNew Balance Womens - White Walking Shoes Size 8.5 (C,D,W) (309502)Lauren Ralph Lauren Brena Women's Fashion Lilac Purple Fashion Sneakers Size 8BMocassins VIDI STUDIO Cuir verni Marron façon Croco T 37 TBEKEEN Mercer Ballerina CNX Red Leather Flat Slip On Loafers Women's Size 8.5 , Womens Skechers Active 22267/BLK Luster Comfort Shoes Womens Size 8.5Womens The North Face Hiking Trail Sneakers Shoes Gray US 9 / , Men's Shoes Slippers Leather slippers Stylish SlippersWomens ADIDAS ZX FLUX W White Textile Trainers S76590$64.99 Reebok Womens S Carter Collection (white / carolina blue) 10-100625Vans Sk8 Hi Slim Neon Pink Leather Women's 9 Men's 7.5 Skate Shoes New NIB , NIB Ted Baker London Vleil Citrus Bloom High Top Sneaker 7, 8 $150VIVOBAREFOOT ULTRA II PINK PURPLE WATER SPORT SHOES WOMEN'S 38 , NIKE AIR Max Women's 2011 [511417-016] Multi Color Athletic Sneakers Shoe Size 7Skechers Women’s Galaxies-Enigma Trainers grey/coral size 6New! Women's Skechers 23303 Microburst - Mamba Walking Shoe - Black N51 , DC Comics Women's Ladies Harley Quinn Slip On Sneaker , Women's Bobs Sport Skechers Bobs Swift-SOCIAL HUSTLE 31354 Silver MemoryFoam New , Nike Tanjun Women’s Size 10 Black Athletic Running Sneakers Shoes F6-218
"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."