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.Wanted Women's Arion Silver ballet Flat 10M***NEW*** Victoria Footwear Suede Tennis Shoes 6 U.S. Made in SpainNot Rated Women's Sandal Black *Mismate* Size Left 8M / Right 7.5MWomen's Skechers Slip On Sport Shoes - Size 11 - WhiteTHERESIA M BOSTON BLACK LEATHER MARY JANE SHOES SIZE 7 US 40 Eur , INC International Concepts Womens Zadde Closed Toe Ankle Wrap Papaya Size 8.0 , M1697L EUC Women's Dansko Belle MultiColor Stripe Canvas Loafer ~~MINT , AGL Attilio Giusti Leombruni Ballet Shoes Black Suede Patent Toe Sz 9 US / 39 EU , **Rocket Dog Canyon Slip On Shoe - Women's Size 9 - Navy , French PIROUETTE by Jane Winkworth Ballet Flat 39/9 Pink Floral Made in France , Banana republic, silver metallic flats, size 8.5, New,Stegmann Wool Felt Clogs Shoes Womens 9.5 Green Holly Holiday Slip OnCamper 37 Brothers Sneakers Women's US Size 7 M Beige Leather Suede Oxfords , Ahnu Brown Womens Causal Mary Jane Shoes Walking Hiking Sneakers 7.5 38Nike Ladies 6/36.5 Zoom Winflo Running Trainers DynamicWeb Athletic SneakersB.O.C Womens suree Closed Toe Mules, Black, Size 11.0 s5cx , PROPET WOMEN'S BLACK LEATHER JOURNEY SNEAKERS -NWOB- NEW SHOES ! SIZE 10!Skechers FLEX APPEAL-OBVIOUS CHOICE Ladies Sports Gym Trainers Charcoal/Aqua -6VANS Authentic Lo Pro (Digi Lightning) Black/True White Women's Low Top ShoesRocket Dog Women's Madox Orchard Canvas Cotton Fashion Sneaker Natural 11 M USAsics Women's Gel Kayano 21 Running Shoe Size 11.5 Preowned , Dr. Scholl's Women's Raven Fashion Sneaker, Castle Rock/Grey, 11 M US , Nike Free 5.0 TR FIT 5 704674-100 White Met. Silver Women's Running Sneakers 9.5Reebok Supreme II Indoor Court Volleyball Squash Mesh Sneakers Shoes Womens 8.5Reebok Classic Leather Walking Cross Training Black Sneakers Shoes Womens 5.5 , Adidas Womens Superstar White Mountaineering Slip On PK Shoe Navy Blue Size 13 , Gola Sport Coaster Metallic Silver Womens TrainersSkechers First Glance Running Women's Shoes Size 5 , New Women's Skechers 11959 D'Lites Looking Glass Walking Shoes Size 6.5 (M13) , Puma Basket Platform Reset - Pink - Womens ,
"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."