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.Skechers Memory Form Slip On's Women's Black Shoes sn 22964 sz 9.5New Womens Black Ballet Flat Gold Studded Slip-on Round Toe Shoes Sizes 6-10 USLadies Down To Earth Slip On Zip Detail LoaferLuxury Rebel Womens Juniper Blue Flatform Loafers Shoes 8 Medium (B,M) BHFO 9486 , Natural Soul by Naturalizer Nerman Women Black Mary Jane Shoe Sz 7.5 M S02I5 , Gianni Bini--- Brown Ballet Flats, Slip-on w/Bows---- Size 6MBirkenstock Slip On Shoes Womens Size 37 US 6 Brown Suede Leather Clogs , Nurture Women's Size 6M Brown T-Strap Mary Jane Comfort Career Low Heel ShoesTeva Womens Niyama Slip-On- Pick SZ/Color. , Clarks Navy Blue Leather Ashland Bubble Comfort Loafer 6.5 SaleEasy Spirit Geinee Taupe Womens Slip-On Size 8M , NWOB Tom's Multi Colored Classic Loafers - 9.5 European 41 , STUART WEITZMAN BALLET FLATS NAVY/BLACK TOES WITH BOWS SIZE 9 USANIKE Cross Training sneakers Womens white leather Size 8.5 Tennis Athletic Shoe2017 HOT Women's Athletic Running Sport Student Casual Breathable Sneakers ShoesSANITA Brown Leather Plateau Knit Cuff Booties Wood Heel Clog Shoes Women 39 8.5Soft Style by Hush Puppies Women's Jaylene Oxford, Black Nubuck, Size 7.5 SDEA , Puma Womens Shoes Sneakers White Purple Future Sport Leather Athletic Sz 6.5 GUCChic Womens PU Round Toe Athletic Slip On High-top Sneaker Flats Sport Shoes NewSide Zipper Chic Womens Athletic Shoes Hidden Height Casual Date Fashion Hot NewHavaianas Slim Crystal Glamour Women's Flip Flops Variety of Colors All sizes , Brooks Cascadia Womens Shoes Size 9 Running Trail Purple Orange Blue 1202041B451ADIDAS NEO ADVANTAGE SNEAKER - WOMENSSkechers Street Women's Mila-Groovy Shine Sneaker, Light Pink, Size 6.0Women's Women's New Balance Sneaker-WRL247FA Year-end Bargain Sale Athletic Shoes , REEBOK YOURFLEX TRAINETTE RS 6.0 SHOE SHOES BLUE M45165 (PVP IN SHOP 69EUR) , $90 NIKE ROSHE GS GIRLS BOYS SIZE 6.5Y FITS WOMENS SIZE 8 NEW 705485 003Vans Womens SK8 HI Slim Cutou Square Perferated Black White VN0A38GQIUZ VaultNew Balance RevLite MRL996JU D Womens Shoes Size 7.5 Grey/WhiteNike Womens Size 6.5 Air Force 1 Light High AF1 Black ,
"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."