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.New Women Qupid Shayan-01 Suede Stencil Pointy Toe Slip On Wrap Flat SizeNurture Slip-on Ballet Flats Comfort Shoes Brown Snakeskin Leather Sz. 7.5 MBELINDA New Fashion Blink Slip On Casual Women Flats Beauty Bowknot Shoes RedTalbots Black Faille Slip On Slingback Flats Women's Size 9 MLadies Spot On Canvas Shoes F8854 , Sperry Top Sider Bluefish Beige Boat Shoes 9276619 Womens Size 6M , Skechers Ballet Flats Black Suede Leather Women Shoes Size 8.5 Medium (B, M)Easy Spirit Black Canvas Low Wedge Slip On Rope Soled Shoes Sz 11MMe Too Proud Black Nubuck Leather Pointed Toe Mocassin Flats 6.5 New , NEW UVS Universe 39 8M brown patent leather oxfords womens ladies flats shoesZara Embroidered Floral Heel Size 39 /8 US , NEW J.Crew Multi-Strap Tartan Ballet Flats Mary Janes Red Black Sz 7.5 $168$70 AEROSOLES WOMENS LOVE BUG SLIP ON LOAFERS BRAND NEWMERRELL Women's 6.5 Grey Mint Green Sneakers Athletic Running Walking Shoe , aetrex X532, woman's size 5 extra wide, silver / purpleWomen’s Outdoor Running Breathable Sports Shoes Athletic Casual Youths Sneakers , Easy Street Women's Kana Mule, Camo, 9.5 N USCROCS Sarah Espresso Brown Suede Soft Fuzz Lined Clogs Heels Womens Sz. W10 $129 , Patricia Green Margo Tri Color Woven Leather Flats Size 9 Black White RedConverse Women Sz 6 Wiener Dog Puppy Chuck Taylor All-Star Shoes Rainbow 114965FSkechers Premium Sport Womens 9 Med Leather 1718 Sneaker Shoes Tan Beige Leather[B39364] Womens Adidas Originals Tubular Strap Sneaker - Pink , ASH VANNA SHERPA LINED HIGHTOP SNEAKERS IN TAUPE 5 , Skechers 12774 Sport Womens Flex Appeal 2.0-High Card Sneaker- Choose SZ/Color. , Vionic Hydra Slip On Sneakers, Women's Size 10, Light Blue , WOMEN'S PUMA VIKKY PLATFORM RIBBON SOFT FOAM PURPLE SHOES SIZE 7.5NEW BALANCE W790LF6 WOMEN'S BLACK/CHERRY RUNNING SHOES sz 6.5 , Size 6 Nike Wmns Zoom Strike Running Womens Shoes Vast Grey AJ0188-006 , Nike IN-Season TR 8 Women’s Size 8.5 Navy Pink Athletic Training Shoes F3-168 , Vasque 7355 Womens Brown Leather Gore-Tex XCR Waterproof Trail Hiking Shoes 11 M ,
"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."