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.Born Copper Brown Leather Oxford Brogue Slip On Flat Shoes Women's 9/40.5MUNRO AMERICAN SPORT JOLIE DARK BROWN PATENT LEATHER LOAFERS WOMEN SZ 9 N ld , MERRELL PRIMO BREEZE II 2 WOMENS SIZE 7.5 BLACK SLIP ON MESH , Womens ALLROUNDER MEPHISTO Red Leather Suede Mary Jane Walking Comfort Shoes 8Lucky Brand Women Clogs LK-Lilac Brown Leather Suede Slip On Peace Sz 6.5/36.5BELINDA Slip On Casual Party Ballet Flats Office Oxford Women Shoes Black 7Propet Womens All LEATHER Mary Jane Sandal Walker-Size 6.5 Nice!HOTTER Abbeyville Womens Loafers Black Leather Tassel Comfort Concept Shoes Sz 9Women Ballet Pumps Leather light pink flat Teens ballerina ,Anniel shoes8 Peach Salmon Beaded Flats Handmade Bollywood Indian Khussa Belly Dance ShoesAGL Women Blue Suede Wedges Size 38/7.5 , Womens sz 6.5 M Vince Camuto Palmira Black Patent Leather Driving Moccasin Shoes , Earth Kalso 7.5 Burgundy Slip On Flats Women'sDr 2 Shoes WOMEN'S COMFORT Orthotic Shoes 9D Wide Style DR9019 BlackNIKE FREE 4.0 Womens 11 RUNNING Gym SHOES Gray ? MagentaSkechers Women's Aura - Sequin Swagger Sneaker,L.L Bean Sport Athletic Hiking Velcro STRAPPY Sandals Size 6 Women's LNSketchers Womens Shape Ups White Silver Walking Workout Toning Shoes Size 9.5Calvin Klein Jaleh Slide Fashion Sneakers 184, Black, 8 US / 38 EU , Nike Tanjun Athletic Shoes, Women's Size 6, Grey/WhiteWomen's Brooks Brothers Beige Leather Flats Excellent Craftsmanship Flats , NIKE Womens Benassi Jdi 343881-107 WHITE Womens Size 6Skechers 49396 Womens Bikers-Commotion Sneaker- Choose SZ/Color.Asics Size 5 M Gel Muse Fit Raspberry Running Sneakers New Womens Shoes NWOBMizuno Maximizer 19 Black/White/Pink 2017 Basic Wide Running Shoes K1GA170101Nike Wmns Free TR 6 Cross Training Womens Shoes Grey Blue 833413-007 Size 9.5Puma Fierce Swan Womens Slip On Mesh Dance Trainers 189885 02 P5 , New Balance Womens 8 Wide 452 Running Training Sneakers White Blue Shoes Leather , Salomon Women's XA PRO 3D CS Pearl Grey/Bordeaux Trail Running Shoes 7MSalomon XA Comp 7 Women's Navy/Black Running Shoe 10M
"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."