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.Liz Baker Womens Brown Leather Oxford Shoe - Size 6MWanted Ignite Women's Nude Slip On Round Toe Ballet Flats US Size 8 , $80 size 7.5 Easy Spirit Georgetta Black Jewels Ballet Flat Womens Shoes , Isaac Mizrahi Live! Leather Moccasin with Bow--- ANABELL---PICK SIZE COLOR NW , Cole Haan Black Leather Slip On Mules Womens Shoes US Sz 10.5Womens Rockport Tru365 Comfort Almond Leather Round Toe Flats Size 7 [SCH0877] , COLE HAAN Chocolate Brown Suede Leather Slides Mules Loafers - Women's 9.5 AA , Reebok Women's PT Prime Runner Athletic Running Shoes.Pick Your Size. CN2031New Balance Womens WL555BA Gray Fashion Sneakers Shoes 12 Medium (B,M) BHFO 9844BCBG MAX AZRIA Women's metallic gray leather Studded pointy flats shoes size 9M , Elizabeth and James Kimi Hidden Wedge Flats Size 7 B Color Blue $198 , ASICS GT-2000 4 Running Shoes, Women's - Size 9, Silver/Blue/Green (Ripped)Men's Rainbow Sandals 302ALTS-SRBR Premier Leather Double Stack Wide Strap , FILA Memory Speedstride RUNNING SHOES Womens 7 , Puma Shoes Comet Love Potion Foam Light Weight Running Mesh Comfortable EUCSkechers Shape Ups 11807 Toning Walking Mary Jane Shoes Women's 8.5 VERY GOOD , Women's Guess Tennis Shoes Ocelot Linden, Fashion Athletic Shoes , New Balance WW577VW Hook & Loop Walking Shoe, White, Assembled in USA, Size 9.5BPropet Women's Harper Leather, EVA Fashion Sneakers, Black, Size 9.5Helly Hansen Women's Seasand HP Flip-Flop Navy/Aqua Blue/Shell Pink/Off WhiteNew Womens Teva Fus-ion Mesh Water Shoes Size 5.5 Grey/Green MSRP $80Women's INOV f-Lite 185 Purple / Blue Trainer Running Sneakers (7)New Kenneth Cole Womens Kayla Black Patent Fashion Sneaker Size 8 , Women's Skechers - Gratis-IN MOTION - Black - New!!! , Nike FLYKNIT ZOOM US Size 7 Green Blue WORN ONLY A FEW TIMES!!Vintage USA CONVERSE Chuck Taylor Teal Blue Canvas Sneakers Boy's 3.5 / Wmns 5.5VANS UNISEX OLD SKOOL METALLIC LEOPARD BLACK SHOES SZ 7 WOMENS / 5.5 MENS NEW , New Easy Spirit Twist7 Slip On Sneakers Medium Blue 9M Shoes NIBKnapp -Women's Allowance Work Shoe-MEMORY FOAM- K524- SIZE 8.5W-NEWNew Balance Fresh Foam Gobi v2 Running Shoes, Women's Size 9 B, Blue/Purple
"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."