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 Propose Spire Leather Printed Flat Women's Shoes 8.5 Brown 26103331Fashion Women's Breathable Girls Recreational Tennis Sneaker Loafer ShoesSpot On Ladies Dolly Shoes Suede Effect Gems F8623 to 8 (R2B) , MUNRO American Loafers Pumps Classics Size 7.5 N , Nicole Miller Grace 2 Ballet Flat- Size 8.5Sporto® Gabby Water-Resistant Clog Slip On Padded Wedge NAVY 10W NEW , Sam Edelman Women's Rockwell Ballet Flat Black Velvet Size 8.0Munro American Leather Loafer Shoe. Size 11 MEasy Street Women's Purpose Slip-On, Brown, Size 11.0 uOoPSperry Intrepid Boat Shoes - Women's Size 6 M, TanClarks Keesha Donna Slides - Women's Size 12M BlackNew Fashion Women's Slip On Casual Pointy Toe Faux Leather New Loafer Shoesisotoner A9B003 Black Plaid Richard Memory Foam Microsuede Scuff Slippers $38Healthy Comfortable Hemp Jute Slippers Flip Flops Thongs - men(14bn)Tahari Womens Gene Black Fashion Sneakers Athletic 6 Medium (B,M) BHFO 5061Classic New Balance *** Turquoise And Pink *** Size 5 Women’s *** , NIKE WOMENS AIR MAX THEA 599409-416 WORK BLUE WHITE DS SIZE: 9Nike ID Shoes Black Leather custom made sz 6.5EMU Australia: Women's Agonis Canvas Sneaker Big Kids/Women (Dark Denim) Size 8New Balance NBGW 1006 Minimus Sport Womens Golf Shoes - Grey/PinkWOMEN'S PUMA FENTY X RIHANNA CLEATED CREEPERS “Puma Black” (366268-04) Size 10.5 , NIKE Women's Air Zoom Pegasus 34 Running Shoes 880560-003 All BLACK Size 8.5 EUC , VANS Chima Estate Pro (Washed) Navy Skate ULTRACUSH MEN'S 7 WOMEN'S 8.5 , Red Wing 2338 Aluminum Toe Women's Work Shoes Size 8.5B Slip Electric ResistantSuperga Women's 2750 Polywool Sneaker, Grey, 7 MSkechers Performance Women's Go Run Forza BOSTON 2016 sz 10 , NIKE BLAZER HIGH 317808-011 Hi Top Sneaker Shoes Leather Metallic Women Size 8.5SESTO MEUCCI HADARA TMORO LEGEND SIZE 7 EUCWomens Hidden Wedge Pumps Casual Sneaker Comfort Athletic Shoes Fashion New&& , Donald J Pliner Women Black Beige 6.5 M Leather Mule Comfort Walking Shoes ,
"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."