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.Soft Style by Hush Puppies Women's Veda Monk Strap Flat, Dark Brown Lizard, 6 2ESANITA "CINDY" FELT CLOSED BACK CLOG/SHOES LADIES US 5 med EURO 36 NEW , NICE Womens Aerology Aerosoles SlipOn Loafers Walking Shoes Burgundy Leather-8 M , VAN ELI Black Oxford Style Flats 7.5 M - SUPER CUTE - CLEAN INSIDE AND OUT!Women's Natural Soul Vasa Brown Wingtip Loafers 16P , New Orthofeet Women's Sarasota Beach Tan Comfort Shoes 10 M NO INSOLE , Vintage Havana Flats Sz 8 Womans Bertie Patched Glittery Slip-On Sneakers Shoes , Merrell Plaza Bandeau Mary Jane Shoes Womens Sz 9David Tate ARF13-110 women's slip on casual career shoe size 8.5 N , MUNRO AMERICAN M555186 RAMIE Womens Black Suede Driving Moc Loafer Shoe 8 NDANSKO Women's Black Leather Mary Jane Strap Over Clogs Size 40 , Flat Jessica Simpson Nalan Nude Blush Crystal Satin , VivoBarefoot Coral Ballet Flat Minimalist Travel Vegan Shoe Womens SIZE 38/ 7.5Bettye Muller Valet Blue Womens Shoes Size 6 M Flats MSRP $175 , Nina Klaire Pointed Toe Dress Flats, Women's Size 5.5M, Dusted Silver NEW , MARCO TOZZI Ballerina Slipper Shoes Pumps Brown NEW , TS shoes TAKING SHAPE sz 9 / 40 Glitter Lexi Sneakers wide fit gold bling NIB! , Hush Puppies Womens Power Walker Sneaker Black Size 7.5 M US EUCJr. Shoes PUMA Suede Classic Fashion Sneaker Black White 5462 01 6 | Converse Chuck Taylor All-Star Women Gray Multi-Color Canvas Sneaker Shoe , Merrell Pace Glove 3 Women's Black Trail Running Shoe 11M , Womens Under Armour UA Size 6 Kick Sprint Track & Field Spikes Racing Shoes Blue , SKECHERS 21361 Womens Walking Shoes Biking Hiking Sport Size 9 , Women's asics womens ngenious And Practical Athletic ShoesNike Air Max Thea Premium Metallic Mahogany 616723-900 Wmn Sz 7 LeatherTods Womens Sneakers Size 7.5 Black Clay T-One Rounded Toe Suede Canvas , NIB Ted Baker London Vleil Citrus Bloom High Top Sneaker 7, 8 $150Rockport Marta Sneaker - Women's Size 6 M, WhiteReebok Classics Women's Size 8 US 38.5 EUR Casual Athletic Shoes White Gray LowAdidas Neo Women's Black White Pink Wedge Heel Dotted Sneakers Size US 9 ,
"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."