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.Calvin Klein Women's Dark Gray Carmela Flat Leather Floral Embellished 8.5 , Womens Shoe Soda Jazzy Open Toe Braided Sandals TAN *New*NEW Women’s The Sak LISA Teal Crochet Driver Slip-on Flats Shoes SZ 6 6.5F0794- Ladies Spoton Diamante Studded Glitter Peep Toe Jelly Shoes 3 Colours , Women's BCBGeneration Curly Black Flats Size 6 M , Boc Born Cocept Mules Womens Size 7 M/W Navy Blue Leather Clogs Shoes Slides , Born Womens Slide Mules Brown Suede Leather Size 9Women's Cole Haan Country dark brown Leather Mules Clogs Size 8B , Anne Klein Sport Tamarow Round Toe Wedge Shoe Choose Sz/ColorMERRELL WOMEN'S STEP ON FLEECE BLACK CLOGS WALKING SHOES CASUAL SIZE US 8.5 , New BORN Size 9.5 STOWAWAY II Silver Gray Ballet Flats Shoes 9 1/2 , WOMENS SHOES-EASY SPIRIT-L2- WHITE LEATHER ATHLETIC SHOE-SZ 9.5M-EUC , Women's Saucony Liteform Prowess Running Shoes Size 9 US , Levis Womens Stan G Canvas Slip On SneakerVintage Nike? Air ~ PRESTIGE II Sneakers ~ 318972-163 ~ Women Sz 6 ~ VERY GOOD , Adidas Womens Cf Superflex W White/Black/Black Running Shoes Size 9.5 (313021)Naturalizer Womens Morrison Black Fashion Sneaker Size 8.5 (2E) (30975)VINTAGE 2007 NIKE REAX WOMENS SZ 8 RUNNING SHOESReebok Womens Fury Adapt Ivory Fashion Sneakers Shoes 9 Medium (B,M) BHFO 6602NEW Superga Shoes 2790 COTROPEW Platform Espadrille Sneakers in NAVY sz US 10NEW Calvin Klein Women's Lyda High-Top Black Sneakers Shoes sz 6NIB Women's New Balance WX00RS Running Cross Training Wide Reg WX00 00 Gray BoxSkechers Performance Womens Go Walk Lead Memory Foam Slip-On WalkingAdidas Women's "Crazyflight X" Boost Volleyball Shoe #BA9269 - NIB - BlackAdidas Running Shoes Sneakers Women Size 9 Multi ColorEcco Black Leather Bluma Toggle Womens Leather Shoes Size US 7-7.5 38 SneakersOn Cloud Womens Hiking Shoes Size 9.5 (3493)adidas Originals Samoa G99719 women's shoes white/silver 100% authentic Size 11Vans New Camden High-Top Black Womens Shoes Size 9 M Fashion Sneakers MSRP $65Women's Nike Revolution 3 Running Shoes 819303-400 ,
"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."