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.LIZ CLAIBORNE LIZ FLEX LADIES BLACK SUEDE SLIP ON SHOES SIZE 9.5 M , Antia MaryJane shoes sz 7.5W low 1.5" wedge burgundy EUC , BELLINI WOMEN'S SIZE 9 BROWN SLIP-ON FLATS LOAFERS LEATHER GOLD HORSE-BIT OXFORD , White Mountain Womens Getty taupe Suede Clogs Shoes Sz 8M , Ladies Shoes Cherry New Black or Grey Leather Zip Up Casual Comfort Size 6-10Bright Cow Leather Oxfords Point Toe Buckle Ankle Shoes Womens Ankle Boots PumpsSANUK Women's Gypsy Rae Jute Cerise Slip On Loafer Sandal Shoes Sidewalk Surfer , Columbia Gray Espadrille Flat Comfort Shoe Womens Sz 11Tahari Womens Frankie Closed Toe Loafers, Black, Size 7.5 xQy3 , Bass Womens Terri Vintage look Leather Tapestry Oxfords Black/ Gold Size 6 , New Womens Clarks Bendables Loafers 66857 (I27)Merrell Womens Size 7.5 Select Fresh Black Suede Slip On Shoes Casual Clogs MuleClarks Womens Originals Faraway Beach Oxford- Pick SZ/Color. , Puma Pulse XT Sport Women's Purple Training Shoes 7MNew Foot Petals Womens Andi Navy Fashion Shoes Size 9 , Fila Womens Shoe Memory Athletic Sneaker Gray Aqua Perpetual Materiality Size 8 , Steve Madden Womens jill Closed Toe Mules, Red Multi, Size 6.5New! Women's Skechers 12764 Flex Appeal 2.0 Metal Madness Athletic Shoe - N51 , Fila Amalfi Logo Perf 5SC60518-001 Black Casual Shoes Medium (B, M) WomenSkechers Go Run Mojo-Verve Sneaker - US 7.5, , New in Box Nike Free 5.0 TR Flyknit Women's Shoes (Size: 5.5, 718785 302, $130) , adidas Originals Women's FLB W Sneaker, Raw Pink/White/Crystal White, 8 ...ASICS Gel Game 4 White PinkMerrell Womens Sz 9 Capra Bolt Blue- Purple Waterproof Hiking Trail Shoes , Women's Nike shoes flex trainer 4 gray/pink size 11 new in boxOrthaheel Vionic Walker Black Leather Shoes Womens Size 8Asics GT 2000 Women's Running Shoes Size US 6 M Purple White T2K7NNike Tanjun Gray White For Women's Youth Size New In Box 818384 003NIKE OUTBREAK HIGH PURPLE VOLT GREY CANVAS CASUAL WOMENS WMNS SZ 6-9 318635-571ADIDAS SUPERSTAR B94463 WHITE SIZE 6.5 WOMEN LEATHER SHOES SNEAKERS MAKE OFFER!!
"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."