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.Women's High Top Rainbow Canvas Trainers Casual Sports Fashion Sneakers Shoes , Sperry Topsider Moc Croc Boat Shoes Burgundy Brown Leather Women SZ 7.5 M , CLARKS Artisan Women's NAVY BLUE Leather Elastic Ballet Flats Slip Ons 7M USDavids Bridal Justin Women's White Textile Peep Toe Low Wedge Ballet Flats Sz 8Easy Spirit Womens Devitt Leather Closed Toe Oxfords, White, Size 8.5 iwIpCLARKS ARTISAN - ROSE PINK FLAT SHOES - 7 1/2SPERRY TOP-SIDER Metallic Platinum Gold Leather Boat Shoes Mocs womens 7M (M9)NIB Bass LAVERNE Black Leather Slip-on Shoes sz 6 M NEWWomen's Skechers 14716/CHAR Go Step Lite- Determined Charcoal , Naot Footwear Retro Brown Shimmer Leather Women's Heels Oxfords Shoes Size 6 MFitFlop Tassel Super Ballerina Black Suede Comfort Moccasins Shoes Size US 5 M , Womens Slip On Pointy Toe Flats Mules Bowknot Sandals Slippers Shoes Casual Size , Women's New Balance 677 Cardio Comfort Gray Running Athletic Sneakers Size 10 BASICS Women's Hyper-Rocketgirl 4 Track & Field Shoe,White/Sapphire/Daffodil,9 BK-Swiss Tongue Twister Tennis Shoes Size 7.5 7 1/2 Med Women's WHITEVolatile Womens Brown Suede Platform Wedge Sneakers Shoes Sz 6 SlushWomen's Mizuno Wave Rider 20 Gray and Pink Shoes Size W 8.5Merrell Barrado Mocha Suede Leather Slip-on Zip Sport Shoes Women's US 7Women's Adidas-Originals-N-5923-W-Iniki-Runner-Blue-Running-Shoes-Sneakers-AQ0268 Economical And Practical Athletic ShoesWomen's LPB Nadia Compensates Taupe Online Outlet Store FlatsUnder Armour Women's Charged Lightning, Glacier Gray (004)/White, 10 , NIB Nike Air Rift Premium QS Shoe Sz 6 , NIB GUESS Maadet Sneakers Logo print White Brown US 10 , WOMEN'S PUMA MEGA NRGY SOFTFOAM BLUE DEPTHS-NRGY TURQUOISE SHOES SIZE 6.5 , Nike Womens Roshe One JCRD Print Olive Flak Black Celery Size 8.5 New RunningNEW JustFab Women's Ainhoa Black Hi-Top Zip Back Sneaker Shoe Size 10 US $60VIBRAM Fivefingers KSO Trek W248 Black Barefoot Running Shoe Sandal 37Skechers BOBS Womens Swift-Zap Zing Fashion Sneaker- Select SZ/Color. , New Converse Chuck Taylor All Star Low Top Tropical Print Sneaker, W10.5 Men 8.5Nike Womens - White Running Shoes Size 9 (419950)
"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."