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 Women Styluxe Lake Faux Suede Pointy d'Orsay Ankle Tie Cut Out Ballet Flat , LADIES SPOT ON FLAT SHOES WITH CUT OUT DESIGN AND BOW (2 COLOURS) F8R0037 , LADIES SPOT ON YELLOW NEON CANVAS PUMPS "F8853" , Via Spiga Lilac Buff Leather Ballet Shoe 7.5 , BOBS NWOB Slip-On Comfort Loafers Size 7 Gray , BOC BY BORN VERY NICE SHOES SZ 7 COGNAC LEATHER MULES MINT , Sperry Top-Sider Womens 8 M Leather Flats Boat Shoes cream/tan , Eileen Fisher Patch 2 Studded Flats Suede Shoes Black Slip on Sz 5.5Anne Klein Womens Noris Gold Metallic Loafers Shoes 6.5 Medium (B,M) BHFO 2027 , New Foot Petals Womens Andi Navy Tennis Shoes Size 6.5 , Nike Free Run+ 3 Women's Shoes Size 9.5 Black Blue Pink Running 510643-064 , PAW-50-05 WOMEN HIGH GLITTER BOOT CAPE ROBBIN BLACK , NEW MERRELL PECHORA WRAP SLIP ON LOAFER SHOES WOMENS 6 J42650 FREE SHIP!Size 6.5 Dolce Vita Cream & Gray Snakeskin w/Tan Heel Pointed Toe Cutout Flats , SKECHERS Womens Shape Ups Black Suede Leather Size 7.5 M Toning Shoes SneakersSkecher Half Sneakers Size 7 TanVIBRAM Fivefingers Sprint W112 Taupe/Putty/Clay Running Athletic Shoe 36Marc By Marc Jacob Size 37 Red Leather Checked Hi Top Wedge Sneakers Shoes 7 US , Women's TRENDY BATTLEFIELD UNISEX SHOES INDESTRUCTIBLE Excellent Craftsmanship Athletic ShoesWomens Nike Zoom Breathe 2K10 - PURPLE/White Running, Cross Training 8.5 M $125 , NIKE Wmns Air Max Thea Sport Fuchsia/Prism Pink Sneakers Size 7 - 599409-605 , Beagle On Black-Women's Running Shoes-Free Shipping*New Womens adidas adiZero F30 TRX FG Cleats Silver/Pink/White MSRP $105 , MBT size 38 1/3 8M Boost Rose white gray womens ladies rocker tennis shoes , Adidas Womens Db0275 Black/White/Carbon Running Shoes Size 7.5 (32042)ASICS GEL-1120V Women's Volleyball Athletics Shoes BN756 Beige Black Sz 8.5Converse All Star CT Gray Peached Canvas Slip-On Shoreline Sneaker Women's US 6 , Bettye Muller x Anthropologie Womens Eve Espadrille Sneakers Lavender Size 36 Neadidas Performance Womens Edge Rc w Running Shoe- Pick SZ/Color. , New Womens Shoes Fashion Casual Sneakers 10 White Skecher Street Uplift Studs ,
"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."