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.Easy Spirit 6 Leather Sandals Shoes Brown Open-Toe Woven Flats Women's 6 NEWKeen Cush Brown Leather Mary Jane Shoes 39.5/9 EUCWomen Sandals Flip Flops Ladies Casual Formal Shoes Flats Beach Wear Size 8 9 10Women’s Size 7 Leopard Print Shoes Faded Glory So Cute! EucLadies Spot On Black Slip On Loafer Shoes F9723 , Joey O Womens Shoes Sz 7 M US Tan Blue Flats Slipons Dress Casual Loafers , Women's Cole Haan 8 B Python Ballet Flats Brown With Black Cap Embossed LeatherSkechers Flattery Transpire Womens Slip Resistant Shoes Slip On/LightweightL'ARTISTE Spring Step FESTIVE Leather Mary Janes Brown Size 37 /6US , LN Think! Artsy Black Leather/suede Size 7 Clogs BlackNaturalizer N5 Comfort Dizzy Buckle Top Coral Patent Slip On Womens Shoes Size 9**Aravon Barbara- Women's Slip on Shoes Black- Size 8DDansko Vegan Valerie Khaki Tan Canvas Mary Jane Clogs US 9.5 /10 Very Nice , Montrail Womens Trail Running Hiking Shoes Fluidfoam size 7.5 Pink and Gray , New Fashion Women's Sports Shoes Casual Shoes Canvas Shoes Comfortable Shoes , Soludos Women's Classic woven tie up espadrille flat candy stripe Size 8 blue , Women's Suede Sweet Bowknot Square Toe Flat Slip On Moccasin Loafers Shoes US SzLanvin Ballet Flat Dark Brown Leather Size 37.5Franco Sarto Women's Hudley Loafer, Silver, 4 Medium US , J Crew d'Orsay Flats 9 Brown Tan Calf Hair Leopard Print Peep Toe Sandals Slides , Sperry STS81945 Womens Seaside Perforated Slip?On Sneaker Sz 8.5 G555 , Saucony - Women's Shadow 5000 HT Sneakers, Black/WhiteSALMING Womens Running/walking/jog Shoes Size 8 M2 EXO Skeleton Turquoise/Pink , Skechers Womens Shape-Ups Sneakers S-8.5 Gray Blue Rocker Toning Walking Shoes , Women's H&M Espedrill Shoes Shop FlatsEnglish Shepherd Print Running Shoes For Women- Free Shipping , VANS ISO 1.5 (Suede) Iron Brown/True White UltraCush Skate WOMEN'S SIZE 8.5Milly for Sperry Topsider Navy Chainlink Shoes Sneakers Sz 9 Womens , Nike Shox Honey Oat Suede Mesh Running Shoes Women's US 8.5M , Cool Style Women's White Platform Shoes Wedge, size 6
"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."