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.NEW Womens SODA OBJECT TAN Flats Slip On Loafers Dress Shoes SZ 5.5 , Unlisted Women's Pop Concert Flat Sandal - Gold - 8 MBlue nn Glitter Sexy Point Toe Comfortable Slip On Women Flats Shoes Size 6Sporto Jasmine2 Faux Fur Lined Slippers, Cognac, 7 US Used , Ladies Flat Low Wedge Loafers Shoes Ladies Slip On WomenWomen's Size 7 BORN BOC PEGGY C80003 Black Leather Wedge Clogs/Mules Shoes *EUC* , Yijie Navy Suede Leather Ballerina Flats Size 37 Made In ItalyIRON FIST LADIES DIGI SKULL SEQUIN PLATFORM SHOES BLACK , J. Crew Womens US 7M Brown Leather Wood Sole Mules Clogs Slip-On Shoes ItalyWomen's Gabor Sport Brown Leather Mary Jane Loafers Sz 9 S37Mizuno Wave Sayonara 3 Women's Size 8 Black Green Teal Purple Running Shoe , GUESS Jeans Shoes Flat Flats Heel Flip Flops Sandals Flop shoe Ballet NIB 5.5NEW PLANET SHOES ELATE WOMENS LEATHER COMFORT FLATS , Brooks Glycerin G13 Running Sneakers Shoes Women's 8.5 Black , Chic Women' Sequine Shiny Sport Casual Sneaker Girls Princess Pump Pu Shoes Hai1 , Simpsons Duff King Velour Full Slippers Novelty Homer Beer Mens Slip On , New! Women's Skechers 22681 Drop In Go Slip-On Sneakers - SIZE 6.5 Black C11Women's PUMA CLASSIC Black Yoga Fashion Sneakers Shoes (Size 7 )Fitness , ASICS Gel-Scram 3 Running Shoe Womens US Size 9 Athletic Gray Cosmo Pink NICE!NEW BALANCE W1140 WT1 Women’s Running Shoes N1221 Color White/Gray/Blue OptimalAsics Gel Noosa Tri 9 Running Shoes Womens Size 6 Pink Purple Yellow , Nike Zoom Hyperfuse TB Basketball White Black Athletic Sneakers Shoes Womens 8.5Nike Air Max Premium 90 Women Size 8.5 Running Shoes 443817 Printed , Asics Women's Gel-Lyte Iii Ankle-High Fashion SneakerMizuno Wave Rider 20 Running Shoes, Women's Size 10 D, Blue , Nike Flex Supreme Tr 5 Women's 852467-001Training Shoes Black/White [145L]Puma Women's Classic Ft Suede Ankle-High Fashion Sneaker , Ryka Luxe Navy Blue Slip on Casual Sneaker Shoe Flats 6 NEWAdidas Nadja Gymnasitcs Bronze Shoes Womens Size 6 Art:017732 , Reeboks Ros Workout TR 2.0 Athletic Shoes - Womens' Size 6.5, Mist/Purple ,
"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."