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.Pure Leather Shoes Women Jodhpuri Flat Sandal Sleeper Embroidery Casual Ethnic , Womens Ladies Sports Casual Sparkly Elastic Strap Slip On Trainers Pumps Shoes , Dr Scholl's SCHOLLS Leopard Pony Hair Leather Sandals Shoes Clogs - SZ 6 M 6M , Footglove ladies size 7 wider fit soft red genuine leather loafers , Talbots Python-Print Leather Loafers - sz 8.5/9Creative Recreation Gold Shiny Satin Fashion Sneakers Shoes Women's sz 7.5clarks women's loafers size 7M Tan leather slip on shoes , Madden Girl Women's Encounter Flats - Multicolored Floral Pointed Toe Shoes 7.5Eastland womens shoes Size 9W Brown Style 3895-02 Kaitlyn Leather upper LoaferStuart Weitzman ballet flats denim pointed toe embroidery women size 6.5 M shoe , Sesto Meucci Of Florence Womens 5.5 Navy Leather Stud Cap Heel Pump Shoe ItalySexy Womens Buckle Strap Ankle Strap Flat Shoes Sandals Pointy Toe Flat Pumps sz , DR SCHOLL'S Double Air Pillow Insoles Suede Slip On Black Loafers Women's 7M , ZIGI Artisan Mallary Slide Loafers 528, White Croc, 11 USEcco Aimee Sport Slip Moon Rock Metallic Coral Womens Flats Loafers 36 / 5 - 5.5COLE HAAN BLACK SOFT LEATHER SHOE ESPADRILLES FLATS SIZE 8 AA , Isaac Mizrahi Burgundy Red Suede Tassel Loafer Flats Paulina NEWSkechers Reggae Fest - Web Of Ties Navy Womens Sneakers Size 6MWomens MERRELL Size 8.5 Bare Access Arc Smoke White Gray Blue Vibram ShoesWomen Flats Mules Slippers Genuine Leather embroidery flower slip on sandals R04 , adidas Adilette CF Cloudfoam Blue White Mens Sandal Slides Slippers AQ3945Nike Benassi JDI Print Grey Anthracite Men Sports Sandals Slides 631261-005 , Saucony Triumph 8 Womens 8.5 Running Shoes Pink Black Gray 10087 AthleticVibram Fivefingers Tree Ascent Womens Sz 7-7.5/38 Black Water Sport Shoes ZV-441Women's Saucony Ride 9 Inexpensive Athletic ShoesConverse Women's Chuck Taylor All Star Shoreline Slip-On Wolf Grey/White/White , Madden Girl Womens PEPEE Hight Top Slip On Fashion Sneakers, Rose Gold, Size 7.0 , Merrell Blue Depths Footwear M Series Womens Size 9 Running Athletic Perf. ShoesNEW BALANCE Women's Stabilicore Silver White Blue Running Shoes WR1226WB Sz 11.5Womens DV BY DOLCE VITA 216247 ivory / peach fabric fashion sneakers sz. 7.5
"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."