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.Rockport Walking Athletic Shoes Size 8.5 Women's , Walstar Women Basic Glitter Mesh Flat Slip on Shoes - Pink , Aerosoles Final Exam Tailored Wedge Womens Size 8.5M Brown Slip-on Loafer ShoesSESTO MEUCCI White Perforated Patent Leather Slide-On Mules Loafer Womens Sz 7NAGATHA-02 Slip On Casual Party Ballet Flats Office Oxford Women Shoes Gold 5Cole Haan Camel Brown Orange Beaded Suede Split Clog Shoe Womens 9 B.A8Stunning Me Too Leather Ballet Flats w/Goldtone Cap And Studded Sides 11M , ANNE KLEIN Women Loafers Block Heel Size 6M BrownWOLKY Leather Ballet Shoes Womens Sz 11 Flats Comfort Slip On $169VANELi Women's Ginebra Ecru Leather Ballerina FlatNWT Sole Society Rosalind Ruffle Pointed Toe Black Suede Flats - Women's 10 MNew Balance Womens WCT780LB White Blue 360 Insole Tennis Sneakers Size 9BGotta Flurt By Merit Destiny Black Womens Shoes Athletic 8.5M , Munich Goal Leather Multi Color fashion sneakers size 6.5BBUCKETFEET Peacock Womens Shoes, Black/Green/White, 6MERRELL WOMENS LORELEI ZIPPER FASHION SNEAKERS SIZE-10 , Asics Gel Scram Womens Trail Running Shoes Aqua/Lime/Gray T2J6N Size 11 , Mizuno Wave Rider 19 Running Shoes Womens Size 5.5 Blue White Athletic SneakersFila Skele Toes Women Size 7 Black White New Shoe Skeletoe Elastic Shoes , Women's Nike Downshifter 6 Running Cross Training shoes size 11 US 684767-002under armour Women's Size 10 Athletic Sneakers shoes micro g Teal Green , Women's Vince Camuto Cariana Leather Sneaker Elegant And Sturdy Package Athletic ShoesVANS Shoes 335462 Blue 23.5ｃｍEasy Spirit Traveltime Women Round Toe Suede Pink Mules (7 M)Converse Women's Chuck Taylor All Star Big Eyelets Hi Metallic Gold/Gold/Wht , NIKE AIR MAX MOTION LW WOMEN'S RUNNING SHOES - WOMEN'S SZ 7Nike Flex Trainer 7 White/Metallic Silver/Pure Platinum/Wolf Grey 98479100 sz 10Womens Skechers Memory Foam RELAXED FIT BIG BREAK slip on walking shoes sneakers , NIKE WOMENS DOWNSHIFTER 6 RUNNING SHOES , Realtree Girl Women's Ms. Bobcat Memory Foam Hiking Shoes ,
"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."