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.Hush Puppies Pearl Carlisle Women's Navy Loafer 9M , New Womens Skater Diamante Zip Loafers Trainers Slip On Sneakers Flats Pumps , Clarks Burgundy Slides Clogs Cordovan Leather Woven 11 NSALE - LADIES SPOT ON ESPADRILLE STYLE SHOES WITH FLOWER PATTERN F2217Natural Soul Women's Black Leather Zip Loafer Shoes Size US 8.5HUSH PUPPIES Womens Tan Leather ALTER PUMP SKIMMERS US-9 (H506147)AEROSOLES UP TEMPO BLACK CROCODILE WEDGE PUMPS SZ 8.5 MSAS Tripad Comfort 2-Tone Bronze Slip On Shoes Coco Patent Toe Ballet Flats 8.5Sigerson Morrison Black Ankle Strap Ballet Flats - size 8.5 , Mojaries Women Shoes Black Flip-Flops Leather Indian Ballerinas US 6-12Seychelles Latest Flat - Women's Size 6, Nude , Fashion Womens Round Toe Faux suede Beads Slip On Loafers Shoes Size AthleticFILA 2017 Hiking Trail Running Sneaker Women US 8 Leather SyntheticNike Flyknit Racer Oreo 2.0 Size 11 DSMaiden Lane Wingtip Leather Low Top Sneaker , SANUK KAT NIP OLIVE SIDEWALK SLIP ON US 9.5 / / NWT , NEW Women's SKECHERS Black Bungee Slip-On All Day Comfort Exemplary Shoes 8 US , Women's Nike Zoom Rival Track Field Shoes Racing Spike Blue 806559-401 Size 9.5 , Nike Shox 324749-111 Turbo VII White & Silver Running Shoes Women's Size 6.5Women's Mbt womens shoes 8.5 Elegant Appearance Athletic Shoes , ASICS Gel Cumulus 19 2A Narrow Width Running Shoes Blue/Purple/Orange SIZE 8 , NEW SKECHERS WOMENS RELAXED FIT EMPIRE GAME ON WALKING SHOEAsics GT 2000 Running Shoes Women’s Size 6.5 US Near Mint ConditionKappa Shoes Caserta Mid V Footwear 3025WL0 C29 Womens Dark Grey Casual Sneakers , Adidas Supernova Women's Running Shoes Sz11 US Blue NWOB , New Balance Womens W590V5 Running Shoe- Pick SZ/Color. , Nike Womens WMNS Genicco Anthracite/Bright Grape/White 644451 005 NIB Size 12 , NEW FREEBIRD BY STEVEN FB927 GRAY BLUE RED WHITE STAR SNEAKERS SHOES SZ 9Women's Skechers Keepsakes Peekaboo Bootie 48803/CSNT Color Chestnut Brand New , VTG VANS OLD SKOOL MADE IN USA SHOES WOMEN'S SZ 5 ,
"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."