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.Kelly & Katie Womens Malindi Suede Closed Toe Oxfords, Light Pink, Size 8.5 1uv3Women’s 11M Sneakers New Canvas Navy Blue with White Stars Mossimo SupplyAerosoles Nuwlywed Women Multi Color Loafer Size 6M , APEX Ambulator Therapeutic Diabetic Walking Shoes Women's Taupe Leather Sz 9 EUCLL Bean Mary Jane Shoes Slip Ons Clogs Womens Sz 7B Burgundy Red Suede LeatherWhite Mountain NEW Size 8 Pastel Green Python Embossed Leather Slip-On Loafer , Vintage ENDICOTT JOHNSON Leather Moccasin Slides Loafers Shoes Size 6M BrazilNaturalizer Women's Kavita Black Leather Slip-On Oxford FlatKlogs SONDRA Women's Clogs Black Smooth Leather Shoes Display Model 11W , Women's KLOGS Non Marking Leather Floral Clogs Shoes 8 M BlackWomen's Merrell Flats - Mimix Daze - Dynasty Green - New!!Steve Madden Excitt Womens Grey Fabric Studded Fashion Sneakers size 10Sesto Meucci Cheryl Black Calf / Dark Tan Bit Loafers Oxfords Flats size 5.5Aerosoles Womens Smart Move Leather Closed Toe Slide, Silver Leather, Size 7.0 ISTUART WEITZMAN BALLET FLATS WOMEN'S 6.5M , NEW Aerin Marion Women’s Colorful Leather Espadrille Flats US Sz 8M Shoes #A108 , ASICS GEL Kayano 16 #T050N White & Teal Blue Track, Running, Athletic Shoes 9.5 , SKECHERS 23325 White Silver Slip On Air Cooled Memory Foam Shoes Women's US 6.5 , Brooks Ghost 7 Women Sneakers Gray Running Athletic Sport Shoes Size 9 B , Nike Training MoveFit Pink Athletic Sneakers Shoes Women’s Size 9 , Teva Sky Lake Womens Hiking Shoes Size 7.5M Purple Brown Spider Rubber-4667 , Teva Women's "Sheeba" Rust & Black Suede Clogs Mules Sz 8 Zipper Athleisure , New Balance 847 v2 Womens Sz 8.5 B Running Walking Shoes GrayWomen's nike shoes women size 7.5 Quality Superior Athletic Shoes , Women's Purple And Blue Vans Quality Products Athletic ShoesAdidas SuperStar II J SCI 078262 Athletic / Casual Sneakers Youth Size: 6.5 , Women Nike Lunarstelos 844736-003 Wolf Grey/Orange Running Shoes Size 6.5 $85adidas by Stella McCartney Clima Cool Running Shoes-Women's size 6.5 WhiteASICS GEL-Kayano 23 Running Shoes, Women's - Size 9.5, Blue/Mint/Pink , New Women's Nike MD Runner 2 Running Shoes 916797-600 SZ 9.5 Red ,
"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."