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.Charles Albert Justeen Flats - Women's Size 6.5, Burgundy , Women's Earth Origins DALLAS Size 9M Loafers Shoes Brown Leather Button Casual , WOMENS SIZE 8.5 STUDIO WORKS BROWN LEATHER LIKE SLIP ON MULES SLIDES BUCKLES , Dr. Scholl's Anna Casual Shoes - Women's Size 6.5 M, GreyB. Makowsky Remi Black Suede Ballet Flats Back Detail Size 6.5Privo 73401 Women's Brown Perforated Leather Mary Jane Loafers Slip Ons Size 7MNEW WOMENS LIFE STRIDE DARK BLUE TIPSY MOC SHOES FLATS SIZE 9.5 M , LADIES SANDPIPER WINDSOR RIPTAPE FASTENING COMFORTABLE CASUAL EVERYDAY SHOESBlack Leather ARIAT ATS Slipon Shoes w/Hidden Elastic Insert 7B (Medium) WesternMerrell Dassie Fold Moc Shoe - Women's Size 8 M, Braken , Adidas Womens Running Shoes Size 6.5 Pink & Lime Green UsedDrew Active Winter White Calfskin Diabetic Women's Walking Shoes 10910-34Sanuk Maisie Women's Shoes Natural Stripes 7 , Nike Air Force 1 Low Canvas 318636-311 Sz. 11 , Clarks Charron Kelly Women's Navy Sneakers 7M , Women's Nike Air Max Fusion Team Gray/Purple Running Shoes 578353-011 Size 7.5Tamarac by Slippers International Opera Slippers - Men's Size 11.5 B, Brown , HAFLINGER Grizzly Torben 43/M10 New! Graphit/CharcoalNew Reebok Womens Yourflex Trainette 9.0 Mt Pink Cross Training Shoes Size 8.5 , Merrell Zip Up Shoes Size 8 Black Mesh Performance Women's , New Balance WX409 Cross Trainer Shoe- Women's Size 10 D, White/Bluewomens merrell hiking shoes size 7 , Costume Triangolo Denny Rose Donna Rosa Leopardato Woman Swimsuit Bikini Leopard , adidas US 8 Blue Mesh Trail Running Shoes Women's , Women's Women's Aetrex Mochaberry Zip-On Shoes Outlet Store Flats , Saucony Echelon 3 Womens Running Shoes Size 7 Eur 38 Silver Premium Trainer , Bearpaw Women's Alana Slipper Slate Blue Wool/Suede Slippers , New Balance 1260v6 Running Shoes-Women's size 6B Blue/Mint , Nike WMNS Zoom Fit PINK Training Running Shoes Sneakers 704658 008 6.5Skechers Sport Women's Flex Appeal 2.0 Insight Sneaker,Black Charcoal,8 ...
"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."