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- TOMMY BAHAMA- SIZE 11 GOLD METALLIC VIONNA SLIP ON LOAFERSEasy Spirit Women's Motion Oxford, Natural Leather, 7 B USKEEN WOMENS BROWN LEATHER MARY JANES SHOES SIZE 8.5 , NEW CABELAS Shoes Womens 7M Light Brown Tan Suede Leather Casual Slip on HikingEasy Street Evette Slip On Clog Flats, Tobacco, 8.5 US , NIB ARIAT MULES LEATHER SLIP ON CLOG BROWN BOMER Retail $59.95ARA Shoes Women's Shoes Shoes Touch Fastener Purple Air Cushion Size 4 1/2 , Jessica Simpson Womens Loranda Leather Almond Toe Ankle Strap Black Size 8.5 X , Soul of Africa Moc Toe Mule Women size 38/7 Black LeatherHush Puppies Size 6 Flocked Detailed Flats , Klogs Cardon Women's Leather Clogs Display Model Shoes Black Wigwam 7 MDonald J Pliner Denny-AP Snakeskin Print Moc Toe Ballet Flat Sz 6.5 M Loafer , Merrell Barefoot Access Arc 4 Running Shoes SZ 7 37.5 Algiers Pilot teal purpleNike 317813-181 Dunk Low womens size 7.5 orange and white Blaze Shock NICE! , JOSHUA*S Mink Fur Leather Slip On Sneakers Size 37 Made in Italy , Sperry Women's Brown Boat Shoes - Size 6M(A-19 ) Pearl Izumi Women's EM Road N 2 v3 Running Shoes Womens SIZE 8 , New Balance Women US 8 White + Pink Athletic Running Walking Hiking Shoes , Chic Womens Wedge Heel Canvas High Top Platform Sneakers Sandals Open Toe ShoesWomen's Chuck Taylor II NIB W6/M4 Excellent Craftsmanship Athletic ShoesReebok Size 10.5 Gray Running Sneakers New Mens ShoesWomens Nike METCON DSX FLYKNIT Cross Fit Training Shoes 849809 011 -Sz 11.5 -NewVibram Women Fivefingers Treksport Sandal Gray Aqua US 6 to 6.5 Brand NewAdidas Unisex Performance Adizero Lj Track Shoe - Choose SZ/ColorVans Sk8 Hi Slim Zip (Hologram) Black/True White-Women's Size 5 , Perry Ellis Womens Brown Walking Shoes Size 8.5 (377731)NEW Ryka Women's Faze Athletic Shoes Slip-on Sneaker Comfort Size US 9.5 M $75Converse All Stars White & Gold Polka Dot Sneakers Shoes Mens 9, Womens 11 , Anna Hindmarch Made in Italy /US 7 Venetian Mirror Bl/Silver Women's ShoesKEDS NEW CONTEMPORY BLACK WOMEN SHOES 18 F/W KWF34100D1 ,
"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."