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.DANSKO CLOGS PROFESSIONAL Black SIZE 10.5-11/41Jutti Indian Handmade Leather Flip-Flops Women Shoes Ballerinas Flat US 5.5 , SAS SIZE 10 N TAN FREETIME COMFORT OXFORD FREE TIME LEATHER SHOES , Women's Ara "Trento" Slip-In Shoes US Size 10 EU Size 41.5 , Sperry Top Sider Intrepid 2-Eye Deck Leather Camel Boat Shoes SlipOn 7.5 MINTClarks Original Wallabee Suede Comfort Desert Footwear Shoes Size 7 Crepe sole , Klogs Martha Womens Clogs Shoes Display Model Leather Black 9 MAerosoles Womens Trend Setter Leather Closed Toe Loafers, Black Suede, Size 6.0 , Merrell 7.5 Beige Slip On Mesh Women'sWomen Ladies Sneakers Waterproof Wedge Heel Causal Breathable Shoes Trainers , Women's Easy Spirit Aubree Navy Blue Slip-on Ballet Flats Size 8.5 W , G by Guess Womens Chippy Fabric Low Top Slip On Fashion, White, Size 7.5 h9Mj , Womens Saucony Raptor TR Gray Running Shoes Size 8M (C200)Merrell Athletic Performance Footwear Size 11 Med- Dark Purple-SHIPS FREE , Reebok Women's Royal Ultra SL Fashion Sneaker Black/Gold Size 7NWOB Woman's Head blue running shoes pink trim 11 sneakersNew Balance 576 [WW576VB] Women's Beige Leather Strap Walking Shoes Size: 9 1/2 , Dolce Vita Women's Dara Ankle Strap Sandal Silver Leather/Elastic Sandals , AHNU SUGARPINE DARK SLATE WATER-PROOF HIKING BOOTS/ SHOES, US 7/ ~NIB , Adidas CC Fresh 2 W Women's Running Shoes S85083 , diesel sherun womens white /orange shoes size8 , Propet Women's Robin Shoe Red 7 XW USNew Cole Haan Womens Studio Grand Blk/Wht Ocl/Blk Fashion Sneaker Size 8 , Skechers Sport Womens Breathe Easy Good Luck Fashion Sneaker- Pick SZ/Color.New Balance Women's 627 Industrial Pink Gray Steel Toe Training Work ShoesAlexandra Collection Womens Size 9 High Top Black / Silver Sneaker Shoes NEW WOT , Vans Sk8 Hi Slim Zip (Leather) Zephyr Blue Women's 7 , NFL-Licensed New England Patriots Women's Canvas Sneakers NWOB Size 7.5New Balance 1870 Rock & Tone Women’s 8.5 B Walking Shoes Sneakers Trainers , New W BOX FILA? Headway 6 Women's Trail Shoes, Navy Turquoise trim, Sz 7
"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."