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.Ladies Ballerina Diamante Casual Pumps Womens Dolly Ballet Mesh Flat Party ShoesWomen's ARAVON BY NEW BALANCE Faux Snake Skin Loafers Brown 9.5 Medium , LADIES SHOES/FOOTWEAR - Step On Air Roma black shoeLADIES TEAL DOWN TO EARTH SHOES STYLE F8R991Vintage Quoddy Women's Native Beaded Cream Leather Handmade Moccasins sz 7LADIES SHOES/FOOTWEAR - Crocs Isabella Jelly flat dk gold/gold , Not Rated Waati Slip-On - Women's 7.5 M, TaupeDansko womens shoes Sz 41 US Crepe suede vintage mary jane clogs , Women's Sperry Top-Sider A/O Black Sequins Boat Shoe 8.5ALEGRIA 'GLEE' LEATHER SLIP ON SHOES MONARCH PRINT SIZE 38 NEW , ARRAY Pixie Women's Slip On, Red, Size 9.0 , Enzo Angiolini Womens Lianne Closed Toe Loafers, Black, Size 8.0 8uUy , Women Oxford Chic Slip on Pearls Slipper Slingbacks Mules Flats Leather ShoesAthena Alexander Womens Taffy Closed Toe Ballet Flats Blushed Size 6.0 wwDBRyka Infinite Running Shoes, Women's Size 6.5 M, Black/TealOn Cloud Flyer Running Women's Shoes Size W7Nike Revolution 6.5 Gray Pink Blue Running Shoes Womensmens slippers brown leather slippers shoes handmade leather clogs flip flopsNaturalizer Womens Marianne Tan Fashion Sneaker Size 7 (C,D,W) (31227) , Vibram WOMEN'S Alitza Loop Fitness Yoga Shoe, Black, 37 Eu/6.5 M UsECCO EUC! Bone White Mobile II Premium Leather Sneakers Shoes Women's 38 (7,7.5)Women's Ladies wearable art shoes Fashionable Patterns Flats , Franco Sarto Women's mony Sneaker - Choose SZ/Color , 2003 Vintage Nike Womens Shox R4 Valentines 302874-611 Sz 6.5 Red/WhiteWomens Brooks Running Shoes Adrenaline GTS Six Size 5 AA NEWBrooks Pure Flow 6 Athletic Shoes - Women's Size 7B - Navy/TealSaucony Grid Omni Walker Athletic Sneakers, Women's Size 8.5, White , Merrell Women's Siren Sport 2 WP, Brindle, 6.5 B USBROOKS GTS 16 Black Pink Silver Running Shoes Womens Size 9.5 MDM B EUC , Womens Adidas Black White Leather High Tops Size 10 ,
"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."