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.Aerosoles Lovely Slip-On Low Wedge Loafers, Dark Blue, 6.5 US , CLARKS Everyday Black Purple Size 10N 1212 Shiny Leather Loafer ShoesSC35 Alisson Casual Loafer Flats, Black, 7.5 US , Tom's Classics Women's Canvas Slip-On Brown , SALE LADIES SPOT ON POINTED TOE SLINGBACK BOW TRIM CUT OUT DETAIL SHOES F8965Dr. Martens Womens Dark Brown Leather 6-Eye Chunky Platform Oxfords 12283 Size 9EASY STREET MARCIE COMFORT WAVE TAUPE IVORY FLATS MARY JANES WOMENS 8 M LN , CLARKS Women's Bellevue Cedar Slip-on Loafer, Burgundy Suede, 7.5 W US , Elizabeth And James Brown Pull On Almond Toe Stacked Leather Petey Riding BootNew Women's Running Breathable Shoes Sports Casual Athletic shoes Hand knit shoeAdidas Woman's cussion tennis shoes size 8Clarks Tripani size 7 1/2 M Black NewReef Pennington Flat White Women's Canvas Shoes Size US 8 /New , New Men Genuine Buffalo Leather Shoes Mule Slip On Sandals UK Sizes 7 8 9 10 11Mens Leather Look Casual Slipper Mules Soft Warm Textile Home Indoor Shoes , Athletic Womens Sneakers Casual Breathable Running Gym Walking Lightweight Shoes , DR SCHOLLS SPLASH Black Gray Sport MARY JANE Waterproof Slippers Sz 9 , Women's Cato Black Canvas Athletic Shoes - Size 5New Vintage Nike WMNS Sprint Sister Running Athleisure 311853-761 Size 9 , New! Womens Skechers 12789 Burst - City Scene Casual Sneaker Gray F24Brooks heritage chariot womens white gray purple running shoes size 5.5 , New Converse Chuck Taylor All Star Brea High Top Women's White Silver 555829cNew Women's Nike Free Inneva Woven Black Sail Size 6 833803 002 , Acorn Women's Summerweight Thong Slipper Bright Madras Slip-Resistant (Non-Skid)Nike Women's Rift Wrap SE Shoes Black/Cool Grey/White 881192-001 Size 7 , Nine West Womens Oranges Suede Fashion Sneaker- Pick SZ/Color.Women's Converse all star Casual Sneakers Metallic Gray Size 7.5 553271C , WMNS Reebok BD1098 Furylite FG Fashion Sneaker FLORAL BLOOM WHITE BLACK GUMLacoste Women's Lyonella Slip 217 2 Sneaker size 7 Blue , 14811 Light Gray GO Run Skechers shoes Women's Sport Mesh Workout Comfort Casual ,
"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."