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.HOLLISTER Cotton Espadrill Flats Women's Size 9 , New handmade Indian women's khussa Slipper embroided rajasthani shoes , RE Mishelle Roma yellow crocodile pattern flat loafer sz 39 US designer , WOMENS CALL IT SPRING FLORINIA ESPADRILLES FLATS MULTIPLE SIZES NEW IN BOXGap Women's Multi-Color Textile Round Toe Slip On Ballet Flats Size US 8 , LADIES SHOES/FOOTWEAR - Step On Air Salt ice/taupe sandal , New Women Refresh Stacy-02 Suede Round Toe Chain Embellished Slip On Ballet FlatSANUK DONNA GREEN KAUAI BLANKET RUG SHOES SANDALS WOMEN'S SIZE 7 NEW WITH TAGS , NEW Ethem Womens Shoes Size 36 6 Brown Leather Open Toe Ballet Flats Casual , Women's Ecco Ballet Green Suede Leather Flats Shoes 38 / 7 -7.5 M , Clarks Gael Angora Ladies Brown Croc Patents Casual Slip On ShoesAetrex Laura Sz 10W Comfort Black Leather Clogs Comfort Shoes LightweightAerosoles Upper Level Slip Ons-Women's size 9 W Pink , Calvin Klein Size 6 Blue Flats New Womens Shoes , LifeStride Women's Isabelle Black Slip On Wedge Shoes - Size 6.5/7 NWB , Sperry Top-Sider Women's Bahama Grey Wool Shoe 12MNaughty Monkey Womens andromeda Fabric Low Top Slip On Fashion Sneakers , Women's Saucony Liteform Prowess Running Shoes Size 9 USTreksta Women's Evolution II Trail Shoe, US Size 6 , Gray (011011) , Merrell Womens Mix Master Athletic Outdoor Trail Running Shoes Size 7.5NEW-REEBOK FURYLITE FG -BLUE W/Pink FLOWERS -WOMEN'S SNEAKERS SIZE 7.5 BD1097 , Report Women's Arvey Sneaker, Bronze, 10 M USNew VAN sayings authentic sneakers shoes women size 8 , New Olukai 20271 DEDE Pehuea Trench Blue Women's Slip On Shoes 7.5 USKenneth Cole Reaction Women's Cheer Floral Platform Sneakers Size 9Propét Women's TravelActiv Mary Jane Fashion SneakerNike Benassi Duo Ultra Slide Women's Racer Pink/Black/Sunset Glow 19717602Superga Women's 2750 Polywool Sneaker, Grey, 7 M , Womens Skechers Relaxed Fit: Easy Going - Repute TPE 49077 #BR , Saucony Swivel Women's Lightweight Running Shoes Sneakers NEW US 7.0
"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."