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.Clarks Artisan Black Ballet Flats Size 6 or Shoes , womens aerosoles beglaration black skin print slip on falts shoes size 7 1/2 , Ladies Down To Earth Leather Casual Shoes with Cut Out Detail Style F3094 , SIZE 5M, BEACON ANTI-SHOCK, SLATE BLUE SUEDE, HIGH TOP SNEAKERS, ZIP UP, FLORAL , Mossimo Ballet Flats Winter White Women's Size 7Crocs Shoes Slip-On Flats Blue Womens Size 10 , Carlos Santana Park Gray Womens Shoes Size 7 M Flats MSRP $69 , Cole Haan Nke Air Womens Shoes Slip On Black Loafers Clogs Mules Size 8.5 B , FitFlop Women's Tassel Bow Sneakerloafer Suede Slip On ShoesBrian Atwood - " Claudelle" Pink Leather Round Toe Loafers Size 9.5 , KLOGS CHANCE CLOGS WOMEN'S SHOES MAHAGONY DISPLAY MODEL SIZE 8 M , DOLCE VITA MAGENTA LEATHER GOLDEN SPIKES FLATS WOMEN'S size US 8 HOTMizuno Wave Legend 3 Pink and teal / aqua running shoes 9.5 USWomen's Asics Gel-Trabuco Gray/Purple Running Shoes Size 7 NICE! , VANS. "Surf Siders" PALISADES Women's Classic Fit Shoes. BROWN US W 10 10.5 & 11 , $79.99 Creative Recreation Womens Galow (brown snake) WCR7547-BRSNKNew Balance 895 Grey with Purple WW895GB Women's Athletics Shoes Size: 12 , Keds Women's Dark Brown and Beige Suede Zip Up Walking Shoes Sz 7.5 FREE RETURN , NEW! Women's BEARPAW Hiking Shoe U14U037A-5 Brown/Turquiose 112N sm , Women's Skechers On The Go 600-15300 Flip Flop Sandal 15300 Color Taupe NewNike Women's Air Max Torch 4 Running Athletic Shoes (White/Mint) - Size 8.5 MWomen's NEW ESPADRILLES WOMENS ESPADRILLES Carmel, Delicate Athletic Shoes , Reebok BS8536 Womens Print Premier Ultk Track Shoe- Choose SZ/Color. , LE COQ SPORTS Omega X Floral Black , VANS Sk8 Hi Slim (Gold Eyelets) Laurel Wreath/True White Green WOMEN'S 10 , Easy Spirit Ap1 White Womens Sport Sneaker Size 9Wwax26 CIABOO shoes red canvas women sneakers , NEW DOLCE VITA WOMENS BRUNO SNEAKERS , NIKE AIR FORCE XXV CLOVERDALE PARK SIZE US 12 NICE SALEREEBOK Astroride Walk Women's Athletic Comfort Shoes Pink CN0857 Sz8-10 SS L ,
"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."