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.Salvatore Ferragamo Womens Luna Visone / Ant Pebble (Browns) Suede 8 AAA , Gap Women's Gold Pink Cap Toe Leather Round Toe Ballet Flats Size US 4 , BOC Born Concepts Womens Sz 6 Loafer Black Slip On , Authentic Handcrafted Shelby Moc Fit Activeflex Women's Leather English Tan 9.5"crocs brown mary jane slip on flats shoes size 7 , LADIES SHOES/FOOTWEAR - SOA Sandal Nikki redSalvatore Ferragamo Gancini Loafers Womens Shoes Boardeaux Leather Horsebit 7 BRangoni Firenze Womens Brown All Leather Size 9AAAA Loafers Shoes ItalyWomen's Size 8 M Sperry Top Spiders G-10 CH196 EUCKEEN TOYAH MARY JANES Womens 8.5 Slip On Shoes Brown Leather Buckle Walking 39 , Adam Tucker Womens Margo Leather Closed Toe Loafers BlackNub Size 9.5 J7nh , Dakota Women's Low-Cut ATCP Grey Hiking Shoe 6.5EENike Sz 10 White Blue & Pearl Tennis Running ShoesWomen's Nike Zoom Winflo 2 Size 8 Black/Green Preowned NICE , Muaa Women's Black/Burgundy Leather Athletic Shoes Size 37 US 6.5 , Womens Grey Canvas Shoes Slip Ons Casual Sneakers Kicks Footwear Tennis FlatsDansko Sz 40 Women's US 9 Black Leather Mary Jane Strap Back Clogs Buckle ShoesWomens Patent Leather Oxfords Flat Special Heels Shoes Rivet Ankel Strappy Shoes , Asics GT 2000 Womens 8.5 Purple Pink Yellow Gym Athletic Run Sneakers Shoes , Women's BROOKS Launch 2 Running Shoes Sz 10 US , Adidas Powerblaze Running C75689 Pink Silver Wht Womens Size 9 , Womens Hollow Breathable Wedge high Heels Creepers Summer Casual Shoes ladyWomen's Fila 5sk60138-147 Exquisite Workmanship Athletic Shoes , Asics Gel-Kayano 20 CORAL RED Womens Size 8.5 , Frye Kira low top sneakers - distressed brown leather rare!- US 9 , Aerosoles Women's Fast Bet Ballet Flat Denim Leather Comfort Shoes , Altra Womens Impulse Flash Pink Running Shoes Size 6.5 (430908) , ASH Women's Black Sequined High Top Ribbon Tie Sneakers Sz 39Womens NIKE DART gray fabric running sneakers sz. 8 ()Nike Womens Cross training Shoes Bn10 black
"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."