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.Clarks Driving Moccasins Size 7.5 Wine Women's Leather Suede Slip On Shoe LoaferSperry Top-Sider Gold Boat Shoes Womens Sz 7 Medium LeatherWomen's Dolce Vita Pavari Snake Skin Flats Size 8.5 M , Skechers BOBS from Womens Plush-Scratch Party Flat 7.5- Select SZ/Color.Cormorant Blue Crittr/Tan Sperry Top-sider Women's size US 11 Eur 42.5 , **Franco Sarto Sela Mule - Women's Size 6 M, BlackVintage Aerosoles Ukraine Navy Leather Casual Flats Rubber Soles w/box 8.5B , Cole Haan Zerogrand Shoes Wing Tip Oxfords 10 B Suede D44060 Black Womens 2E2New Balance 813 Women US 6.5 Gray + Pink + White Cross Training Shoes WX813 , Women's RBX Marty Gray Athletic Sneakers Size 7 BWomen's Skechers 21511 Biking Running training Shoes Size 8.5NIKE FREE TWIST LITE PURPLE LIME WOMENS 7 V-NICE V-CLEAN see pics-details , ASICS Gel GT-1000 Gray with Pink Running Shoes Women's Size 9 T4K8N , Vionic Alliance Black Casual Orthotic Diabetic Walking Shoes Women's Sz 9Women's VICTORIA Sneaker 1141109 Noir Sale Price Athletic ShoesWomen's PUMA Evolution Mostro Women’s Shoes Exquisite (in) Workmanship Athletic ShoesWomen's NEW CUPLÉ WOMENS BALLET FLATS Outstanding Features FlatsNike Womens Air Zoom Pegasus 34 880560-602 Women Running Shoes Pink $110 SIZE 8SKECHERS Uplift Street LA Wild Thang Fur Zebra Platform Shoes Sneakers Womens 6 , Nike WMNS Roshe LD-1000 women lifestyle sneakers NEW black summit white , NEW IN BOX WOMENS NIKE AIR ZOOM STRONG SHOES SZ 12 CROSSFIT TRAINING 843975 301Propet Women's Tami Casual Shoe Grey/Silver Size 7.0 , New Womens Green & Blue Nike Classic Ultra Flyknit Tennis Shoes, Size 8Nike Free RN Motion Flyknit 2017 Black Volt Pink 880846-004 Women's Running Shoe , PUMA Roma Basic Women's Black/Black 36414203Easy Street Women's FabulousSkechers Shape-Ups Shoes Sz 10 Silver Blue Fitness Toning Walking Womens , ASICS Womens Gel Cumulus 18 AquaSplash/White/PinkGlow Running Shoes Size 9.5Nike White Blazer SE Summit #AA1557-100 Sneakers Womens Size US 9M , Puma Carson 2 Molded Women's Running Shoes Black/White 190036 03 Sz6-10 K ,
"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."