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.New women size 9M CROC ballet flats black , LIFE STRIDE Women's Fancy On Shoes, Size 6, Black Pre-owned VERY GOOD CONDITION , Born Brand Oxford Tie Shoes Brown Leather Sz 8 WAsos Black and Clear Brogue Oxfords 7 , Women's Aerosoles Flats - Betunia - Black Snake - New in Box!Ladie Clarks Ordell Becca Tan Or Black Leather Casual Mary Jane Style Shoes , COLE HAAN GARNET II DRIVER FIERY RED SUEDE LEATHER WOMEN SIZE US 8.5B HOTMARCO TOZZI Slippers Court Shoes Lacquer Artificial Leather Black NEW , Vaneli Women's Gray/Tan Suede Slip-on Perforated Moccasin Flat Size 6MWomen's CLARKS Black Leather Suede Sneakers Walking Shoes Size 9M , Vans Women's Galaxy Print Low Top Sneakers 721356 Multi-Color Size 6.5 , Nike Jana Star Blue white Cross-Country Running Shoes 314957 441 Women Sz 9 , Mizuno sz 9M Wave Rider 8 white navy blue womens ladies running athletic shoesNew Balance WW577 Hook and Loop Sneakers-Women's size 8.5(2E) White , Altra Womens Impulse Flash Pink Running Shoes Size 8 (424178) , New Merrell J09654 Bare Access Flex Paloma Women's Running Shoes 11 US , Nike Jordan Express GG White Black Kids Boys Lifestyle Shoes Sneakers 897989-109Nike Air Force 1 Flyknit Low Women's Shoes, 820256 004 Size 6.5 NEWNike Air Huarache Run Ultra Se Black/Gray And Vachetta Tan Sz 10Nike Lebron James X 10 Easter Mint Green White 543564-303 Women's Sz 7.5/Kids 6YWomens Nike Lunarconverge 852469-002 Anthracite/Hot Pinch Brand New Size 9.5FILA J314R White Green Multi-Color Women Running Shoes Sneakers 5-J314R-130 , SKECHERS Memory Foam Women’s Athletics Shoes, Black Size 6 .....S24 , Women's Skechers 23452/BKW Galaxies - On-Air Casual Shoe Black/White Brand NewNew Balance Women's W775V2 Athletic Running Shoes Grey/PurpleChristian Audigier Womens Shoes Gray Orange Green Suede Fashion Sneakers Size 7 , Newton Running Shoes Women's size 6.5 Cross Training Pink YellowWanted Shoes Women's Gramercy Fashion Sneaker,Burgundy Size 7.5M US , New Balance WW577VK Leather Hook and Loop Walking Shoe Size 12 Needs Inserts 2A , WOMEN'S PUMA PLATFORM SNEAKER Sz 9 White GOLD GENUINE LEATHER VIKKY SHOES * NEW
"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."