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.G by Guess Womens 11 Ballet Flats Black White Leopard Cheetah Animal Print ShoesThe Flexx Womens Rise N Curry Tan Ballet Flats Shoes 9 Medium (B,M) BHFO 6926Lucky Brand Womens Emmie Blue Ballet Flats Shoes 8.5 Medium (B,M) BHFO 7805gloria-33 New Fashion Comfort Ballet Slip On Casual Office Women's Flats ShoesDexter Brown Leather Uppers Loafers Shoes Comfort Women’s Size 9M USAnaturalizer Saban Slip-On Loafers 091, Black Leather, 5 US / 35 EUSkechers Womens Bobs B-Loved Round Toe Loafers, Black, Size 6.5 KRYjJessica Simpson Women's Lafayette Ballet Flats Black KidSuede Size 6M , Aldo Womens Harmony Ballet Flat- Pick SZ/Color. , Munro American Women's Fabric and Leather Slip On Shoes ~ Dark Gray ~ US 10M , AGL Bow Patent Leather Flats Sz 10.5 US 40.5 EU Nude $325Salvatore Ferragamo 7.5 Black Flats VintageLadies Padders Casual Extra Wide Fitting Shoes - Daisy , Shellys London Black Leather Kimmie Peforated Platform Oxfords Women Size , Womens Nike Max Air Extreme Volley Volleyball Shoes Sz 10.5 Black SilverNEW WOMENS LADIES REEBOK SHOES WHITE LIGHT GRAY ATHLETIC YOURFLEX TRAINETTE 11Skechers Women's Go Step Lite Black Mary Goga Max shoes Sz 8.5 black () , Keen Palisades Hikers Trail Hiking Walking Shoes Leather Mesh Women's 9.5 BrownWomens Low Top Loafers Pull On Canvas Casual Runing Sneakers Casual Comfort Shoe , Women's Modern Fiction Ballerina Crazy Price, Birmingham Flats , NEW BALANCE CLASSICS WOMEN'S WRT580AK SORBET PACK GREY RAINBOW CORAL SIZE: 6 , Nike Women's Volley Zoom HyperSpike Volleyball Shoes NIB Size: 12.5Adidas Ultra Boost ST W Purple Size 10.5 Women’s US AQ4430 Running Shoes , NIB! $130 Womens Nike Air Max Zero 857661 001 sz 6.5 Grey sneakers runningSneakers and Athletic Free People Naples Slip-On Sneaker WhiteOnesole Women's Native Rocks Collection Multicolored , Clarks Vailee Frost Black Leather Bungee Strap Sporty Walking Shoes 9 SALENike Womens Tanjun Black Running Shoes Size 9.5 (30798) , Women's NIKE FLEX TRAINER 7 898479 White+Gray Athletic Casual Sneakers Shoes NEW , Superga 2750 Cotu Classic Black, off white trim. 11 Women’s, Men’s 9.5 ,
"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."