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.JOSEF SEIBEL LADIES/WOMEN SHOES BROWN LEATHER SIZE EURO 40 US 9.5 CRINKLE/STUDSWomens Franco Sarto Axel Black Patent Leather Open Toe Heels Shoes 6 1/2 M VGCBarefoot Freedom Mule Women’s Brown Leather Walking Casual Size US 6.5 , Rocket Dog Daines Casual Shoes - Women's Size 9, Indigo BlueWomen's Franco Sarto Granite Shoes Black Leather Ankle Boots Size 5 M NEW! , Nine West Womens Antonecia Leather Closed Toe Loafers, green Suede, Size 9 m , Stuart Weitzman Womens Brown Leather Suede Size 7 Slip On Mules Loafers Shoes , ECCO Devine Moc Suede Penny Loafers, Women's Size 7-7.5, Coral Blush , Frye Melanie Flats US 9M Brown Leather Loafers Slip-on Shoes Women A6Dr. Scholl's Beatrice Leather Slip On Shoes, Women's - Size 7.5 M, BlackSkechers BOBS from Women's Chill Luxe Flat Brown 8 B(M) US , Womens IVANKA TRUMP gold sparkly fabric ballet flats sz. 5 $110Calvin Klein Floral Studded Mule Flats 749, Almond Tan, 6.5 US / 36.5 EU , Mephisto Womens Cool Air Loafers Sz 9.5 Brown Leather Slip OnDiesel Industry Women’s White & Pink Textile Upper Sneakers Shoes Flats Sz 9.5 , New Womens Embroidery Floral Mesh Breathable Sneakers Breathable Loafers ShoesSudini Women's Black Suede Leather Fashion Sneaker, Black, Size 12 M Orig.$139.Vans AUTHENTIC SLIM (Scarf) Black/True White Women's Shoes 9.5Merrell Women’s Siren Breeze Vibram Hiking Shoes Size10Brooks Trance 12 Womens Running Shoe Size Eur 41 Black/Pink , Women's nike womens running shoes High Quality Athletic ShoesWomen's NEW..SANITA..SHOES 5 BORDEAUX..SIGNATURE,.PROF. SHASTA PATENT..LEATHER Easy-to-clean Surface FlatsMarc By Marc Jacobs GRRL Black Suede Slip-on Sneakers Women's Size US 8.5/ , ADIDAS WOMENS SUPERSTAR WHITE/CHALK CORAL CG5462 , Healer Sneakers Athletic Shoes 6 Korean White Green Walking Toning Korea Healers , Nike Zoom Rival Track Racing Shoes Baby Blue 806559-401 Womens Size 12Women's Lowa S-Cloud WS Chestnut/Olive Size 9.5 MSRP 140$ , Asics Womens T762N GT-2000 5 Trail Athletic Running Cross-Training Shoes Sz 9.5WOMEN'S PUMA SUEDE CLASSIC TURQUOISE MINT/WHITE 355462-32NEW BALANCE "WARRIOR" Womens White LACROSSE Cleats Turf Shoes WBWT-LW NWT ,
"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."