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.AGATHA-02 Synthetic Diamond Slip On Casual Women Flats Office Shoes Black 5***Ann Taylor Women's Gold Leather Slip On Ballet Flat Shoes US Size 10 MDANSKO Sage Green Suede Professional Clogs Comfort Shoes Women's Size: 39 / 8 , Reef Womens SALTY ISLAND FUR Closed Toe Loafers Dark Grey Size 9.0 kMRqDi Sandro Black Heels size 39 Buckle Square Point ToeBUGLE BOY Mens 7 VINTAGE Grunge 90s Black Oxfords Chunky School Unique Rare r5RARES BOTTILLONS KICKERS T 39 NOIR TBE A ACH IMM FP RED MOND RELAY A VOIR !EASY SPIRIT 'Walktos' Black Suede & Mesh Comfort Loafers Walking Shoes Sz. 9W , Salvatore Ferragamo 9 Black Loafer Women'sArtemis Anthropologie Silk Velvet Loafers Woven Flats Smoking Slippers Sz 41 , Sam Edelman Womens Francis Black Ballet Flats Shoes 6 Medium (B,M) BHFO 6075 , Women's Skechers Shape-ups Walking Shoes Size 10 Brown Leather Mary Janes , Chaps by Ralph Lauren Ingrid Black Oxford Brogue Wingtips Shoes Womens Size 7B , LADIES HI-TEC CASUAL SHOES (CHARCOAL/PLUMNESS) - STYLE SIERRA LITE ORIGINAL , Nike AIR FORCE 1 '82 Women's Size 7 Y Athletic Shoes 031012 Black Leather UpperAcorn Fave Gore Slipper - Men's Black Tweed XLNew VANS Authentic lo pro sneaker shoes Bittersweet/Blueprint women size 5.5 , adidas Performance Womens Vigor Bounce w Tennis Shoe- Select SZ/Color.Women's New Balance Running Shoe 7Skechers Womens - Black Walking Shoes Size 8.5 (362480)Nike Air Max 180 White Silver Blue Women’s Size 8.5 Running Shoes , K-Swiss Classic VN Low Athletic Shoes Women's Size 5.5, White 958Merrell Womens - Brown Trail / Hiking Shoes Size 8 (326184)ALDO Women's Cassis Fashion Sneaker, White, Size 7.0Nike Women's Cortez Leather BEAUTIFUL x POWERFUL JOAN BENOIT BLACK 884922-001 7Nike Women's Zoom Strike Running ShoeWOMEN'S ADIDAS ENERGY VOLLEY BOOST 2.0 SIZE 14 !! BRAND NEW WITHOUT BOX! , WMNS NIKE DUNK LOW SKINNY VNTG SIZE 6.5NIKE Free Run+ 2 EXT Women's Running Shoes US 6.5/NEW/DisplayNEW Balance 608v4 Women's White And Pink Size 9.5 9 1/2 ,
"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."