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 Merrell Ortholite shoes Mary Janes size 7.5 brown$90 FALCHI DARCEY Coral Gold Suede Designer Comfort Ballet Flats 6 , BOC. Born Concepts Women's Shoes Mules Clogs Loafers Black Leather Wedge Sz 9 MVintage Dexter USA Womens Size 6 & 1/2 Brown Leather Keltie Tassel Loafer Shoes , Sami-27 New Fashion Slip On Casual Party Flats Office Winter Warn Women's ShoesCandie’s Rhinestone Bravo Pewter Espadrilles Women's Size 7.5 WovenClarks Brown Leather Women's Slip On Comfort Loafer Flats size 8 M , Brinley Co Women's Nadia Ballet Flat Black Size 6.0Isaac Mizrahi Dannie Navy Blue Leather Bow Ballet Flats NEW , Sanuk Womens Blanche Prints Slip-On- Pick SZ/Color.Jambu Bailey Women's Clay Slip On Strap Mule Flats US 8 M Shoes B486 , Cole Haan Studio Beige Slip On Mules - Size 7C , Skechers One-up Women's Formal Black Textured Ballerina Style Work Pumps New , Sperry Top Sider Women's Shoes Size 6.5 M Brown Leather Boat Shoes Deck22063 SKECHERS WOMENS SPEEDSTERS CASUAL SNEAKER BlackWomen Saucony Cohesion 10 Gray Running Shoes Size 8 M D224Nike Air Max Motion LW SE Women Sz 8 Gray Running Training Athletic Shoes F5-144 , Converse All Star Chuck Taylor Shoreline Sneakers - Women's Size 7, WhiteQupid TERRACE-02 Black Colorblock Knit Mesh Low-Top Platform Athleisure SneakerNike Wmns Flex Essential TR Black White Women Training Shoes Trainers 924344-001Womens Nike Free RN Distance 2 Hyper Violet Dark Shoes Sneakers 6.5,7,8.5,9.5Puma Size 11 SMASH PERFORATED METALLIC Black Leather Sneakers New Womens Shoes , Puma Womens Fierce Rope VR Velvet Black White Pink Gym Trainers Shoes 190347-01 , Carlos Carlos Santana Alegra Slip-On Fashion Sneakers, BlackMEHOTO Womens Fashion Lightweight Tennis Walking Shoes Sport Air Fitness Gym 8.5 , ECCO Stitched 6-Eye Athletic Fashion Sneakers Women's EURO 41 (US 10.5)New Balance Womens - Purple Running Shoes Size 11 (415693)NEW WOMEN'S NIKE ROSHE LD 1000 SNEAKERS BLACK 819843-001 SIZE 9 , New Hush Puppies Womens Classic Walker White Leather Sneaker Shoes The Body Shoe , Vibram Fivefingers Women's V Run Running Shoes Size US 6 ,
"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."