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.Sporto Jasmine 2 Faux Fur Lined Slippers, Black, 9 US UsedNew Women AD2S Black Taupe Vegan Suede Mary Jane Ankle Strap Ballet Flats , INC womens 6 black mesh studded embellished ballet flats shoesTRANSAT BOUTIQUE BALLERINES "ILOUNA" TAUPE 37 - PRIX PROMO! , Frye Womens 8.5 M Carson Ballet Flats Brown Leather Shoes 3472126 elSofft Wedge Sandals Shoes Women's Size 7.5 N Brown Leather Open Toed Classic , Sperry Top Sider, Women's 6M, Plaid Multi Color Loafer Boat Shoes, 9561457Andrew Geller Black Leather Mary Janes, Size 4.5B, CUTE, SEE NOTES , Minnetonka Cally Red Suede Leather Slipper Moccasins Womens Size 8RARE DVD ASIE CELINE DION SUR LES PLAINES , DIMMI, JOGGER FASHION SNEAKER, WOMENS, BROWN PONCHO, CANVAS, NEW WITH BOX , NEW Banana Republic Womens Flats Shoes Leather Ashley Ballet Copper 9.5 $118 NEWStuart Weitzman Women Shoe Size 7N Narrow Black Croc Patent Leather Loafer WedgeBOBS from Skechers 31423 Womens Phresh-Phresh Flowers Fashion Sneaker , DEMONIA SPR02/FLFA Platform Lolita Heart O-Ring Platform Mary Janes Floral ShoesNaturalizer Brittany Ballet Flats - Women's size 9 N - Black , TODS Women’s Dark Brown Leather Penny Loafers Driving Shoes SIZE 37.5 , Asics Gel-Frantic 5 Women's Running Shoes - Size 9.5 - Black, Silver, TurquoiseAll Star High Top Gray Canvas Unisex Trainers-size 9.5-Converse , Saucony Ride 5 Running Shoes, White/Pink/Silver, Womens US Size 11 , Brand New Women's Savannah Printed Denim Sneakers - Mossimo Supply Co , Womens Pull On Low Block Heel Pumps Shoes Flats Loafer Bowknot Decor Square new , Merrell Circuit MJ Black Suede Casual Mary Jane Hiking Sport Shoe Women Size 6.5New! Women's Skechers 12404 Empire - Heart to Heart Walking Shoe - Grey/Mint O39Women Adidas Original Gazelle Athlethic Tennis Shoes Size 9Womens Size 11 Multicolor Nike Zoom Vomero 7 Running Shoes 511559-050 preowned , Asics Gel Unfire TR Running Shoes, Women's Size 7.5, White/Blue , Nike WMNS Benassi JDI [343881-104] Women Sandals Slides White/Grey-BlackAsics Gel-Rocket White Silver Running Shoe Women's US 10 Eur 42 (P2,1)Women's Skechers Empire-Sweet Scene Taupe 12413/TPE With Air-Cooled Memory Foam
"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."