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.Gianni Bini Studded Sandals Worn Once Size 7M Retail $98Ten & Co Shoes NWOB Sizes 37, 38, 41 RRP $179.00Crocs Beige Mary Jane Comfort Shoes Flats Size 5AR35 Cellia Ballet Flats 398, Black, 8.5 USNew Women Mary Jane Ankle Strap Ballet Flats Criss Cross Shoes Black,TaupeGroove Women's Tomorrow Ballet Flat, Natural Rio, 8 M USSperry Top-Sider A/O 2-Eye Blue Womens Shoes Size 5 M Flats MSRP $95NIB Cole Haan Amalia Gray Storm Lizard Flats 6 M Retail $200Naot Black Ankle Strap Mary Jane Women Sandals US 6NEW Catherine Malandrino Women's Tuxedo Penny Mules Loafers Slides Metallic 7.5 , Kenneth Cole Ken Slip On Sneaker - Women's Size 6.5M, Black , Nike Zoom Pegasus 31 Athletic Sneakers Running Training Shoes Women Size 7 , REEBOK DMX Shear Running Womens Size 10 , RYKA ~ NEW $87 BROWN SUEDE LEATHER ATHLETIC SHOES SNEAKERS MULES 7 W NEW NIBNIKE FLEX EXPERIENCE RN 4 RUNNING SHOES / MULTI COLOR ( SIZE 9 ) WOMEN’SWomen's Asics GT-1000 Size 11 Sneakers Shoes Running Green Pink Gray Gel T15 , Fashion Korean Women's Oxford Casual Flats Sneaker Heels Breathable Shoes SW23 , Womens LA Sportiva Trail Mountain Running Shoes Ergonomic Size 7 , Asics? ~ GEL-VENTURE 6 Athletic Shoes ~ Everyday T7G7N ~ Women Sz 8 ~ VERY GOODCloudsteppers by Clarks Step Allenabay Slip On Sneakers 377, Grey, 8 US / 39 EUNEW ADIDAS BARRICADE CLUB SZ 6 MESH WHITE/SUNGLOW ADIWEAR/ADIPRENE ATHLETIC SHOE , Valentine's Day Special-Heart Print Running Shoes For Women-Free Shipping , Women's Nike Dual Fusion Running Shoes NEW MSRP $110 , Converse Grey Boots and Black Leather Fur lined woman's shoesadidas alphabounce em W BW1196 size 9.5 shoes Chalk White , Converse All Star Woven Knit Shoes RARE Gray Black Pink Chuck Taylor Sz 9Skechers Women's Glider Forever Young Black/White Athletic Shoes-Size 7.5/9 NWBNew Skechers 14958 NVW You Rise Navy Blue / White Women's Slip On Shoes 6.5 US , VANS Authentic (Late Night) Black/Hamburgers Food Women's 5Women's Mizuno Wave Nirvana 8 Running Shoes Sz 9.5 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."