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.Womens Ralph Lauren Shoe/Loafer/Flat Slip on w Buckle Leather Size 6 B Like NewAnne Michelle L4936 Ladies Black Flat Dolly Shoes w/Shiny Toe Cap (R32A)(Kett) , Traditional Flip-Flops Women Shoes Leather Jutti Flat Ballerinas US 5-10White Mountain Womens Praise Closed Toe Oxfords, Gold/Metallic, Size 9.0 fYvB , Madeline Stuart Women's Perforated Ballerina Flats Size 8 W Round Toe With BowNWOB Kenneth Cole Reaction Blue Flats Size 10Ladies Down To Earth Flat BallerinasTom's Classics Women's Canvas Slip-On Shoes - Size 6Womens Size 8.5 Merrell Jungle Moc Brown Leather All Terrain Sneakers , Nine West Womens Stefany Suede Ballet Flat- Pick SZ/Color. , Bandolino Womens Yara Pointed Toe Slide Flats, Red, Size 8.5 CLdtWomens Asics GT 2150 Running Shoes, Size 9.5 , Deer Stags Nordic Slippers - Men's Size 10W - Black/GreyNew Women's VANS Tazie SF Gossamer TAN Casual Shoes US Size 9Converse All Star blue purple satin stars sneakers size 7 , Keds Womens Size 10 Shoes Athletic Sporty Comfort slip On Casual Sneakers BrownNew Bella Vita Womens Emilie DarkBrownSuede/PlaidFlannel Fashion Shoes Size 9.5 , Le Coq Sportif Omega X Satin Womens Turtle Dove Textile Trainers , Adidas Women's Galaxy Trail Running Training Shoes CloudFoam Sneakers NEW , Easy Spirit Punter White/Light Grey Womens Sport Sneaker Size 9W , NEW SKECHERS GO RUN PACE OMBRE SNEAKER SHOES WOMENS 6.5 LIGHTWEIGHT FREE SHIPNIKE Women's Air Zoom Pegasus 34 Running Shoes 880560-003 All BLACK Size 8.5 EUC , Superga Women's 2388 Leaw Fashion Sneaker - Choose SZ/ColorAdidas CloudFoam Womens Size 7.5 7-1/2 Black Shoes Sneakers Running HWA 1A3001SAS Tripad Comfort Wmns 9.5 NARROW Beige Leather Shoe USA Walking Sneaker Oxford , New Balance 1540v2 Running Shoe Size 6.5 Women's Green Gray Athletic 1L1Steven Natural Comfort Women's NC- Nellie Perforated Sneakers TW4 Grey Size 8.5Vans Black/Gray Checkerboard Wo's 7.5/M- 6 Suede/Canvas High Top Trainers ~Excel , Women's Nike Free TR 7 Reflect Training/ Running Shoe Sz 10 USALDO Pryven | Fashion Sneakers | Red | Size 7.5 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."