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.Shades of Brown Snakeskin Pattern Faux LeatherNATURALIZER N5 Comfort Flats 6.5 MDonald J. Pliner Block Heel Loafer Womens Size 7.5 M Brown Slip On Square ToeNaturalizer Womens Sidney Square Toe Loafers, Brown, Size 9.0 z0Kx , Sexy Womens Flat Slip On Shoes Horsebit Leather Rabbit Fur Lined Mules ShoesWinter Women Platform Shoes Fashion Ankle Boots Martin Boots , Anne Klein Zilya Elastic Espadrille Flats 936, Metallic Tan/ Tan, 6.5 US , EASTLAND women's leather mules clogs slip on SHOES BLACK sz 6M B3Easy Spirit Women's Eliana Mule Dark Natural/Brown Suede all sizesWomen's Cole Haan Avery D42294 Beige Flats Size 9.5 M , Jack Rogers Womens Camille Sparkle Pointed Toe Flat- Pick SZ/Color. , Clarks Ladies Indigo Charm Black Leather Shoes UK Sizes 3 x 9 (R10A) , Fila RN 91175 Women's Athletic Running Shoes Multi-Color Size 9.5 Memory Foam , Nike Women’s Training Gray With Flurorescent Green Swoosh Sz. 9.5 , Women's adidas Original's Shoe White Size 7.5 , Jack Rogers Women's Regina Ballet Flat Caribbean Blue/Midnight Size US 7.5M I83Tory Burch Ballet Flats Soft Black Felt w/ Patent Leather Gold Buckle - Size 8MAdidas Baseline Casual Sneaker - Women's Size 7.5, White/BlackSaucony Ride 7 Women's Running Shoes Size US 7.5 B Silver workout S10241-2 Q1WOMENS NIKE HIPERCLAVE LITE SHOES 528900-600 RED sz - 9.5 NEW WITH DEFECT , RJ's Fuzzies? Barrow Mens Fleece Lined Leather Driving Slipper Black Size 11 , $119.99 PF Flyers Womens Vere (lime green) PW09PP1H , SKECHERS Go Walk 2 Hypo Slip On Casual Shoes, PPL/Black, Womens US 8.5 , Salomon XR Mission 1 Women's Size 6 Athletic Shoes SneakersNew Vintage Nike WMNS Sprint Sister Running Athleisure 311853-761 Size 6 , womens purple SALOMON XR MISSION shoes running sport trail 9.5 MWomen's Multi-Color SHOES WOMENS SIZE 8 Superior Quality Athletic Shoes , Easy Spirit Traveltime Navy White Womens Clogs Size 8MReebok BD2047 Womens Stylescape 2.0 Arch Fashion Sneaker- Choose SZ/Color.Puma Suede Classic + Blur Women's Limited Edition~ Drizzle-Fair Aqua , OLUKAI WOMEN SHOES SIZE 10 NEW
"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."