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.Women’s Easy Spirit Size 6 ½ Slip-On Casual Shoe, Brown Suede & Textile , Lands' End Womens Size 5 Blue Suede Mary Jane Casual Shoes , TROTTERS Navy Blue Woven Leather Flat Slip On Loafer Shoes Liz Women's 7New Women Nature Breeze Boardwalk-02 Snake Leatherette Boat Loafer Flat Sz 6-10VANELI Women US13N Black Leather Loafer Unique Multi Color Cap Toe & Heel Dress , NWOB Hush Puppies 'HPO2' Black Loafers - 9 European 41BOC Born Margaret Closed Back Clog Women size 9 Brown Leather , TORY BURCH Black REAL LEATHR w/Gold LOGO Disk & Elastic-Back FLATS Shoe (EUC) 7M , White Mountain Womens ALFRESCO Fabric Closed Toe, OffWhite/Black, Size 7.5 , Teva Hydro - Life Slip On Women's Sz 6 Granite Blue Waterproof Shoes Outdoor NEWWolverine 1883 by Women's Alice Slip-On Shoe Black Size 7.0 , Easy Street Womens Campus Leather Closed Toe, Grey, Size 9.0 HLXxNew J Slides Womens Pollie Blush Fashion Shoes Size 6.5NEW IN BOX women CLEATS shoes sz 10 ASICS Hyper-rocketgirl 5 white/fuschia/greenSalewa Hike Roller GTX Running Mountain Hiking Shoe Women's 7.5 Carbon EmeraldNike Free 5.0 Flyknit Run Training Athletic Shoe 615806-614 Women 9.5 USHush Puppies Women's Labsky Elastic Sport Sandal, Teal, Size 9.0ASH Bowie Suede Wedge Sneaker / Clay / Size US 8 , Clarks Women's Shoes Collection Soft Cushion Brown Suede Size 9 M NEW OTHER , $90 Size 7.5 Merrell Encore Brown Suede Bracken Shoes Slip Ons SandalsAhnu Sugarpine Athletic Shoes - Women's Size 8 - Blue Star , Saucony Hurricane ISO 3 Sneaker - Women's Size 9 Gray/Blue , Skechers Performance Womens Go Flex Train Commit- Pick SZ/Color. , Palladium Pampa Hi Stone Dk Khaki Taille 37 , K-Swiss Classic VN Aged Foil Edition Women's Sneaker Shoes Gold 93744-282 , Vans Old Skool (Black Outsole) Montana Grape Women's 9.5 , Salomon XA Comp 7 Women's Slate Blue/Deep Blue/Dahlia Running Shoe 9M , Under Armour Spine Glyde ST Women's Black White Softball Cleat Shoes (11)Nike Rosherun Print Leopard Purple Pink Shoes Sneakers Running Women's Size 9 US , CONVERSE ALL STAR WHITE GOLD POLKA DOT SNEAKERS WOMENS SHOES SZ 10 NEW DISPLAY ,
"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."