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.DANSKO CLOGS PROFESSIONAL Black SIZE 10.5-11/41Lucky Brand Women's Gray Moccasins Loafers, Size 10 US, MM , Carlos by Carlos Santana Women's Vegas Black Flats Size 8 MFitzwell womens shoe Black 7.5M Leather uppersClarks Collection SZ 9.5 Womens Black Ballet Slip On Leather ShoesClarks Unstructured Un Poem Womens 6.5 M Blue Leather Mary Janes Loafers Shoes , TORY BURCH Russell Green White Woven Leather Bow Tassel Flat Shoes Women's Sz 7M , Donald J Pliner 8.5 Black Gold Leather ballet Flats Cap Toe EUC Career , Rockport Total Motion V Cap Leather Ballet Flats, Women's Size 5M, BlackComfort Women Low heel Open toe Hollow out Back zip Roman College Shopping shoesZumba Impact Pulse Z Slide Shoes - Coral/Gunmetal , ECCO WOMENS COMFORT WALKING OFF WHITE LEATHER ATHLETIC SNEAKER US 8 - 8.5LifeStride Women's Nexus Fashion Sneaker, Dark Grey, 6 W USSteve Madden Womens Black Leather Wedge Tennis Shoes Size 8 MWomen's Mizuno Wave Sky 2 Running Shoes size 7 B Regular Width worn onceWomens Mywear High Top Shoes Floral Flowers White Size 6.5Saucony Womens Grid Ridge TR2 trail Running Walking Shoes Sz 6.5 traction q10 , Women's Ellie Women's Pirate-418 Outlet Store FlatsWomen's Shoes PUMA Cell Riaze Athletic Sneakers 188028-01 Silver *New*NEW Converse DC Comics Chuck Taylor All Star Hi 152599C Harley Quinn joker shoesNike Rosherun Wmns 511882-678 Women's Casual Shoes Last Sz 100% AUTHENTIC Rare , Nike Air Huarache Run Ultra Bone Orchid Sz 7.5 $115 Brand New , puma vikky platform ribbon rapture rose Free Shipping , Academie Gear Women's KristinNEW NIKE REVOLUTION 3 WOMEN Running Training US 5.5 SHOES 819303-014 , Adidas Stan Smith VULC Shoes White/Green Skate B49618 Sz Men 6 Women 7KENNETH COLE NEW YORK WOMEN'S KINGVEL CLASSIC WHITE LEATHER SNEAKER - NEW SHOESAsics Gel LYTE33 Women's Running Shoes Lilac/White/Flash Yellow Size 10Skechers EZ Flex Shoes Walking Athletic Memory Foam Air Cooled Taupe Sz 8 9 NEW , Women's Skechers 31361/CCOR Bobs Sqaud?Tennis Shoes Charcoal/ Orange ,
"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."