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.All Occasions Gold Flats Size 10Sperry Top-Sider Casual Leather Boat Shoes Women's US Size 8m Beige Tan Classic , Women’s 11M Sneakers New Canvas Floral Print Blues Red Greens Mossimo Supply , Dr Doc Martens England Mary Janes Strap Womens sz 6 Black Leather Clog S1Nine West Womens 7 Round Toe Leather Loafer Flat Antonecia Shoes Black Slip-OnBass Judy Woven Leather Clogs Women's 7M Mules Wedge Shoes Slip On Stitching EUC , Sanfrediano designer woman jean & leather embelished shoes 36/US 6 Made in Italy , SAS Tripad Comfort Walking Shoes - Black Leather ~ Women's Sz 10 N ~ Narrow , Naturalizer Clarissa Loafers-Women's size 8 W BlackSperry Topsider Women's Water Boat Slip On Shoes Navy Flat Heel Size 7MCLARKS BLACK SLIP ON WEDGE HEEL LOAFERS SHOES WOMENS SZ 7.5 MWomen's New Balance 1011 Nergy Sneakers US 9.5 B Sz Very Clean! Nice ShapeNWT WOMEN'S VANS AUTHENTIC LO PRO (POP) SNEAKERS/SHOES.SIZE 7.NEW FOR 2018!Cole Haan Black Suede Patent Cap Toe Ballet Flats Shoes Women's 6.5Everlast Sport Women's Black Lauryn Athletic Running Shoes Size 9MRyka Womens - Gray Walking Shoes Size 10.5 (344822)Fila Womens Rosazza 2 Walking-Shoes- Pick SZ/Color. , Womens Sport Sneakers Breathable Athletic Walking Shoes Casual Comfy TrainersSkechers Women's Go Joy 15602 Walking ShoeAsics Gel Nimbus 18 Running Shoe, Women's - Size 8.5, Grey/TealAsics Gel-Nimbus 18 Blue Neon White #T650N Running Shoes Women's Size US 7.5 , **Skechers Double Up E.MOE.G Slip on Sneaker - Women's Size 8, Black , Women's Cobian Hanalei Flip Flop Sandal HAN17-690 Color Coral 100% Original NewNew Balance 571 Womes Sz 10 Running Walking Cross Country Workout Gym Shoes , Vasque Trail-Running Shoes GT-2000 5 Women's Aluminum/Sliver/Orchid 11MKeen Targhee II Hiking Hoes, Women's Size 9.5, BrownNew Women's Skechers 11729 Flex Appeal Sweet Spot Training Shoes Size 6W (N18)Salomon XA Pro Women's Pearl Grey/Bordeaux/Hot Pink Running Shoe 7.5M , New Balance Womens Wx1267pp Blue Running Shoes Size 6.5 (358262)Women's Salomon Speedcross 3 Outdoor Running Sports Training Shoes 18 Colors ,
"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."