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.Womens Girls Black Flat Loafers Shoes Driving Moccasin Pumps School Work OfficeLuichiny Womens Vay Kay Blue Casual Shoes Sneakers 10 Medium (B,M) BHFO 7646 , Elefanten Womens mules slides Shoes Size 36 6.5 Blue leather slides floral , Munro American Lauren Women's Bronze Leather Slip On Loafers Flats 7.5 SS , The North Face Face Women's Navy and Green Lite Skimmers (SZ 7) Y321 , RF Room Of Fashion Anna-21 Mary Jane Back Bow Decor Ballet Flats PINK PEARL PUDIMMI, ZEN FASHION SNEAKER, WOMENS, DUSTY ROSE, LEATHER/FABRIC, SIZE 7, 8.5 NEWOld Beijing Cloth Embroidered Shoes Plum Blossom red , Dije California Women's Brittany Moccasin - Size 7, BlackKeen Black Ballet Flats Slip On Buckle Shoes 9 Canvas Womens Floral Pattern , Wanted Arion Womens Silver Ballet Flat shoes 10M , women's shoes OLGA RUBINI 8 () moccasins slip on red paillettes BX786-38Klogs Women's Clogs Display Model Shoes Astra Partridge Square 8.5 M , FRYE COMPANY LEATHER BALLET FLATS EMBER BORDEAUX WINE SIZE 7 , Enzo Angiolini Liberty Leather/Patent Leather Top Comfort Flats Shoes Size 6M , New Wonder Comfort Womens Comfort Boot in Black Colour Size 6 , Ecco Biom Performance Train Running Womens Shoes Sz US 10-10.5 White Purple Gray , Merrell Connect Women's Size 6 Black Blue Vibram Running Athletic Shoes ZU-235Womens NIKE Flyknit Lunar 2 Running Trainers 620658-414 Sz 9.5 US BlueMerrell Black Purple Performance Sport Zip Slip On Sneaker Womens Size 8.5 , Women's Seychelles Women's Even Better Sneaker Exquisite Workmanship Athletic ShoesNIB Women's Nike Flex Experience Rn 4 Prem 749177_102 RN SupremeNew Balance Fresh Foam 1080 Black/White Running Shoe Women's US 11 Eur 43 (H2,8) , Womens Brooks Ghost 10 Mesh Cushioned Trail Running Athletic Shoes Size 8 , Walter Genuin LINEA STRETCH Slip On Leopard Golf Shoes ITALY Size 10.5?New Balance FuelCore Urge v2 Size 7 B Women's Running Shoes Sneakers WURGELX2Women's Vans Sk8-Hi Moc Suede VN000315JU1 Port Royale/Blanc de Blanc Brand NewNike Womens Hyperdunk 2013 TB Basketball Shoes Size 11 Green 599527-300CONVERSE Chuck Taylor All Star Ox Off White Snake Woven Low Top Sneakers 9.5THE NORTH FACE WOMEN FASHION SNEAKERS US M M MULTI-COLOR LEATHER ,
"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."