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.Sperry Top Sider Seamate Rose Boucle Patent Leather Boat Shoes Size 7 M , AXXIOM Kourtney Women's Black Cut Out Casual Comfort Slip On Flats Size 6 NWOB , COMFORTWELL BY BEACON Faux Patent Leather Bow Flat Slip-On Shoes - Size 7MGreat Pair of Women’s Beige Sperry Top Sider Shoes Sz 6Groove Womens Bohemian Western Faux Sheepskin Suede Moccasins Shoes Black Size 7Pajar Womens Astrid Canada NAVY Open back Mule Slippers sz 8.5M (39) - NIB,RV$95NEW Nautica Bryn Womens Faux Leather Loafers Shoes Dark Brown MSRP$50Trotters Women's Liz Pewter Woven Leather Slip On Loafer Size 7.5M (T5158-584)Cole Haan metallic bling flat sz 6 B D42274 , NWT Massini Women's Size 8 Black Velvet Rose floral Embroidered Loafers ShoesLisa for Donald J Pliner Flat Beautiful Snake Design Flower on top SZ 7 Beige , Family Pajamas Men's Christmas Holiday Reindeer Slippers, RedNEW BALANCE 413 SL-2 Running Shoes Women's.. size.6 B , 03-85 New Balance Black Sea Salt WL696SKG Women's WALKING SIZE 9.5BAdidas Women Shoes Training Sports Essential Fun 2.0 Walking Running BB1527 NewNike Flex Trainer 2 Women's Athletic Gym Sneaker Shoe Purple Size 6.5 , New! Womens Skechers 11717EW Synergy Trend Setter Athletic Shoes Black B33 , converse 555853f ctas hi white black white free shippingPUMA Women's Basket Heart DE Sneaker Blue Depths/PUMA White Classic ShoesNew Balance WW928HW2 Hook and Loop Walking Shoes - Women's Size 8.5 B, WhiteVibram FIVEFINGERS CLASSIC Womens Black W108 Athletic Casual Shoes , Puma Roma Metallic W Black Dark Shadow Womens Fashion Sneakers 360977-01 1703-61 , Converse Star Player Ox White Athletic Navy Womens Trainers Unisex New , Onitsuka Tiger Womens Mexico 66 Slip-on Sneakers Aluminum/Aluminum Size 11.0Women Adidas BY9237 Court vantage casual shoes gold black sneakers , Royal Elastics Icon x Andox Box 1707 Andy Lau Black Leather Women Shoe 92073-999 , Skechers Women's Go Step-Challenge Walking Shoe , Diadora Women's Swan Running Shoe - Choose SZ/Color , Roxy ARJS600369 Womens Flamenco Mid Fashion Sneaker- Choose SZ/Color. , DVS Women's Edmond WOS Skateboarding Shoe, Black Canvas, 7 M US ,
"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."